Certain pesticides can become ineffective if used repeatedly in the sa

I totally hate this question, and generally start cursing uncontrollably when my students miss it. But I'm cursing at the question -- NOT my students -- because I think the question is ridiculous.

But as usual: the GMAT doesn't really care what any of us think. Let's solve this SOB.


"One reason is suggested by the finding..." Seriously, GMAT? Who the hell writes like that?!

But remember our two-step technique from the SC Guide for Beginners: eliminate DEFINITE errors first, then look for meaning issues. I don't think that this muddy mess is DEFINITELY wrong. The semicolon correctly separates two independent clauses, and the comparison seems OK.

"One reason is suggested by the finding" is awkward and wordy, in my opinion. But that's just my opinion, and my opinion doesn't matter -- and no matter how awesome you are, neither does yours.

Keep (A), perhaps while holding your nose.


I'm comfortable getting rid of this one right away, because of that very first phrase: "if used repeatedly in one place" would need to be followed by "pesticides," not "one reason." (B) is out.


(C) has the same issue as (B), plus that comparison seems a little bit off: "much larger populations of pesticide-degrading microbes are found in soils with a relatively long history of pesticide use than those that are free of such chemicals." "Than those" would be better if it said "than in those." (C) is out.


This isn't horrible, to be honest. Well... actually, yeah it is, but so is (A). I don't think there's a DEFINITE error in (D), but the placement of "if used repeatedly in one place" is definitely suspect: it sounds like "one reason" is the thing that is used repeatedly in the same place. You basically have to re-read the whole thing to figure out that it's the pesticides that are used in one place.

More generally, I think you could make a (not super-convincing) argument that the sentence is so horrendously wordy that you lose track of the subject. "The finding (blah blah blah....) is suggestive of one reason...." In general, please be really careful with this sort of thing. Frankly, (A) is pretty wordy, too; (D) is arguably wordy enough that the meaning become unclear. That's a judgment call, and that's really not the way you want to think about SC, but it maybe adds a little bit of support to the idea that (A) is better than (D).

If you wanted to be conservative, you could keep (D), but I think that the modifier placement issue definitely tilts us toward (A). So (D) is out.


I actually really like the placement of "if used repeatedly in the same place" here. And I think we can make a similar (weak!) case about "wordiness" as in (D): there's a whole lot of stuff between the subject and the verb, and that makes things muddy. But again: you shouldn't be terribly convinced by arguments about "wordiness", and we should try to find something that's more solid, relating to either grammar or meaning.

And here's the big issue: "the finding of much larger populations of pesticide-degrading microbes..." We're really not talking about the "finding of microbes" -- that would refer to the act of seeing the microbes themselves. The "reason" that we're interested in is the finding that there are larger populations of microbes in some soils than in others.

And I know: that's subtle as all hell, but it definitely makes the meaning in (E) a little bit illogical. So we're left with a steaming pile of poo, otherwise known as answer choice (A).
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(A) Certain pesticides can become ineffective if used repeatedly in the same place; one reason is suggested by the finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals. --- Can't lay hands on this choice. The topic is split with a semicolon, a sensible thing to do in such cases.

(B) If used repeatedly in the same place, one reason that certain pesticides can become ineffective is suggested by the finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals. -----The participial modifier - If used repeatedly- should modify pesticides and not one reason

(C) If used repeatedly in the same place, one reason certain pesticides can become ineffective is suggested by the finding that much larger populations of pesticide-degrading microbes are found in soils with a relatively long history of pesticide use than those that are free of such chemicals. -----------The participial modifier - If used repeatedly- should modify pesticides and not one reason

(D) The finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals is suggestive of one reason, if used repeatedly in the same place, certain pesticides can become ineffective.----- The sentence is a run –on. The second part of the topic, going after - if used repeatedly – is dangling loosely without a connector such as that or a semicolon. Hence, wrong

(E) The finding of much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in those that are free of such chemicals suggests one reason certain pesticides can become ineffective if used repeatedly in the same place---- As in D, a connector as –that- is essential between reason and certain.
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Dear Friends,

Here is a detailed explanation to this question-

Meaning is crucial to solving this problem:
Understanding the intended meaning is key to solving this question; the intended meaning of this sentence is that certain pesticides can become ineffective if used repeatedly in the same place, and one reason for this phenomenon is suggested by the finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals.

Concepts tested here: Meaning + Modifiers + Comparison

• In the “phrase + comma + noun” and “noun + comma + phrase” constructions, the phrase must correctly modify the noun; this is one of the most frequently tested concepts on GMAT sentence correction.
• A comparison must always be made between similar elements.

A: Correct. This answer choice uses the phrase "the finding that", conveying the intended meaning - that the fact that there are much larger populations of pesticide-degrading microbes in certain soils than in others suggests one reason for the given phenomenon. Further, Option A avoids the modifier error seen in Options B, C, and D, as it makes use of neither the “phrase + comma + noun” or the “noun + comma + phrase” construction, thus conveying the intended meaning - that the pesticides are used repeatedly in the same place. Additionally, Option A correctly compares the prepositional phrases "in soils with a relatively long history of pesticide use" and "in soils that are free of such chemicals".

B: This answer choice incorrectly uses "If used repeatedly in the same place" to modify "one reason", illogically suggesting that one reason for the given phenomenon is used repeatedly in the same place; the intended meaning is that the pesticides are used repeatedly in the same place; remember, in the “phrase + comma + noun” and “noun + comma + phrase” constructions, the phrase must correctly modify the noun.

C: This answer choice incorrectly uses "If used repeatedly in the same place" to modify "one reason", illogically suggesting that one reason for the given phenomenon is used repeatedly in the same place; the intended meaning is that the pesticides are used repeatedly in the same place; remember, in the “phrase + comma + noun” and “noun + comma + phrase” constructions, the phrase must correctly modify the noun. Further, Option C incorrectly compares the prepositional phrase "in soils with a relatively long history of pesticide use" to the pronoun phrase "those that are free of such chemicals"; remember, a comparison can only be made between similar things.

D: This answer choice incorrectly modifies "one reason" with "if used repeatedly in the same place", illogically suggesting that one reason for the given phenomenon is used repeatedly in the same place; the intended meaning is that the pesticides are used repeatedly in the same place; remember, in the “phrase + comma + noun” and “noun + comma + phrase” constructions, the phrase must correctly modify the noun.

E: This answer choice subtly alters the meaning of the sentence through the phrase "The finding of"; the construction of this phrase incorrectly implies that the act of finding much larger populations of pesticide-degrading microbes in certain soils than in others suggests one reason for the given phenomenon; the intended meaning is that the fact that there are much larger populations of pesticide-degrading microbes in certain soils than in others suggests one reason for the given phenomenon.

Additional Note: Please note the difference between "the finding that" and "the finding of": in "the finding of", "finding" refers to the act of literally finding something, and in "the finding that" "finding" refers to the results of an investigation or to certain information that has been uncovered.

Hence, A is the best answer choice.

To understand the concept of "Phrase Comma Subject" and "Subject Comma Phrase" on GMAT, you may want to watch the following video (~1minute):



All the best!
Experts' Global Team
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Under the limited conditions A is the BEST but where is option (E)?
Kindly post the OA and OE and option (E)

if in A it had been one reason for the same ....is suggested ... it would have been better construction

(A) Certain pesticides can become ineffective if used repeatedly in the same place; one reason is suggested by the finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals.

(B) If used repeatedly in the same place, one reason (wrong subject for the first phrase) that certain pesticides can become ineffective is suggested by the finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals.

(C) If used repeatedly in the same place, one reason (same as B) certain pesticides can become ineffective is suggested by the finding that much larger populations of pesticide-degrading microbes are found in soils with a relatively long history of pesticide use than those that are free of such chemicals.

(D) The finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals is suggestive of one reason, if used repeatedly in the same place, certain pesticides can become ineffective.--there are -(redundant)

(E) The finding of much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in those that are free of such chemicals suggests one reason certain pesticides can become ineffective if used repeatedly in the same place ---(microbes comparison- Incorrect)

Hello,

Could you please help me understand the below ? two questions.

Certain pesticides can become ineffective if used repeatedly in the same place; on reason is suggested by the finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals.

I broke down this questions into its repective clauses correctly as below:

Certain pesticides can become ineffective if used repeatedly in the same place;

on reason is suggested by the finding

that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils

that are free of such chemicals.

1) the first that clause, I agree it modifies the finding and because of that reason I thought it was incorrect because isn't the finding singular so why I have the verb are here? I know the article there is here to complement the verb are, but there are is still refering to the finding ? My main issue is that relative clause that is refering to the finding and i thought it should be singular

2. why is E incorrect ? per the OG explanation, it is not clear what the finding is refering to. Insn't finding refering to what is coming right after ? a much larger populaton of pesticide-.... I chose E since I thought it was more concise.

please help me clear my thoughts. I did this question twice and chose the same wrong answer E.

Thanks for posting your question here Aris

Before I answer your query, I want you look at the following sentence.
a. There were many apples in the basket.
b. This is a car.

Can you see how the singularity/plurality of the verb in the above sentences is determined?
“There”, “This” etc. act as “Placeholder pronouns” and do not directly act as subjects. They simply point to a particular object somewhere. (Aha! There it is!)
Verb is singular/plural depending on what the verb is linked to.

As you can see, in example (a) the verb is linked to “apples” and hence we use the plural “were”
Similarly in example (b) the verb is linked to “car” and so we use the singular “is”.

Now let us come back to the question on hand. I hope you might have noticed already that we use the plural “are” because of the plural “populations”.

The clause “there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils” answers the question “What reason is suggested by the finding?” and “that” simply acts as a “connector” here.

To answer your second question, please provide your detailed analysis on what you understood about the sentence and what errors you found in each option so that we can correctly identify where you are going wrong. This will minimize the number of queries and save time for both of us.

Thanks for cooperating with us.

Regards,
Krishna Chaitanya
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thank you!. yes, I got the point with there are and there is. Thanks! When I saw that clause, I automatically assumed whatever comes after must refer to the word it modifies. But both the meaning and the struture makes sence.

The POE analysis I did for the remaining answer choices were similar to those suggested by OG explaination on e-gmat SC.
B and C both have modifier errors: If used repeatedly in the same place is modifying one reason.
D has a modifer error too. If used repeatedly in the same place.. is not clear which clause it modifying

E I still dont really understand it. I broker it down like this, not use if it s correct. I really dont see the meaning error. Please help me really see what wrong with this answer choice ?

-The finding of much larger populations of pesticides-degrading microbes in soils with a relatively long history of pesticide use ( here the finding is the subject)
-than in those that are free of such chemicals suggests one reason ( here in those refers to soils, the other ones, those free of such chemicals meaning those soils that dont have long history of pesticide use. So i didn't think there is paralellims error. Also, suggests is the verb of the finding which is singular. That is the pronoun holder that refers to soils and are is the verb. soils is plural so are is correct)

-certain pesticides can become ineffective if used repeatedly in the same place (certain pestices is the subject and came become the verb and this makes sence)

I dont really see the meaning error. The finding of X suggests one reason certain pesticides can become ineffective ?

Hi Aris,

Let's once gain begin from the beginning. Let's understand the meaning of the original sentence Choice A:

Certain pesticides can become ineffective if used repeatedly in the same place; one reason is suggested by the finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals.

First let us understand what is this "finding". The "finding" is that "certain pesticides can become ineffective if they are used regularly in the same place". The part after the semicolon in the sentence then elaborates on one of the reasons of this finding.

With this understanding, let's now analyze Choice E:

The finding of much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in those that are free of such chemicals suggests one reason certain pesticides can become ineffective if used repeatedly in the same place.

In this sentence, the meaning is distorted because now the sentence says "much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in those that are free of such chemicals" have been found. This has been said to be the "finding". Is this the same meaning that we got from the original sentence?

The finding is that certain pesticides can become ineffective. And then the reason has been mentioned. But per choice E, now the finding itself has changed. And this is why this choice is incorrect.

Hope this helps.
Thanks.
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In B/C, "If used repeatedly in the same place" directly refers to "one reason". So straight wrong.
D is run on sentence as part1 "The finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals is suggestive of one reason" and part 2 "if used repeatedly in the same place，certain pesticides can become ineffective" can act as independent sentences.
E needs the linkage(preferably that) between "one reason" and "certain pesticides can become ineffective if used repeatedly in the same place"
A is fine...... as it is devoid of all these modifier and connector issues.

Certain pesticides can become ineffective if used repeatedly in the same place; on reason is suggested by the finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals.

Please find below the clauses in this sentence :

Certain pesticides can become ineffective --- IC

one reason is suggestedby the finding ----IC

That there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals---IC


Now my doubt is what is 'That' modifying in this sentence. Is it modifying 'findings' or 'reason'. Logically it should modify reason because the reason for the finding is that 'there are much larger......'. Moreover the clause after semicolon is written in passive and we we turn it into active than it will read as- The finding suggests one reason that...-
. Now it is clear that 'that' is modifying reason. Is my analysis correct?


I

A semi colon separates two independent clauses. The part before the semi colon and after the semi colon are two independent (but related) clauses.

The last part of the sentence "there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals." is the finding, not the reason. The finding suggests the reason.

Take a generic case: You notice A (A - Certain pesticides can become ineffective if used repeatedly in the same place)
You wonder why A happens. You are looking for a reason.
You notice B. B is something you find by testing. B is a finding. (B - there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals)

B suggests you the reason for A.

So 'that there are ... such chemicals' is an essential modifier of 'finding'.
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Hi Rahul,

Thank you for posting your doubt here.

Let's break this official sentence in its clauses:

Cl. 1: Certain pesticides can become ineffective if used repeatedly in the same place; (IC)

Cl. 2: one reason is suggested by the finding (IC)

Cl. 3: that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils (DC)

Cl. 4: that are free of such chemicals. (DC)

In this sentence, "that" refers to "finding" as its give detail about what that finding is. So yes, "that" refers to "finding".

Hope this helps.
Thanks.
Shraddha
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[quote="egmat"]Hi Rahul,

Thank you for posting your doubt here.

Let's break this official sentence in its clauses:

Cl. 1: Certain pesticides can become ineffective if used repeatedly in the same place; (IC)

Cl. 2: one reason is suggested by the finding (IC)

Cl. 3: that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils (DC)

Cl. 4: that are free of such chemicals. (DC)

In this sentence, "that" refers to "finding" as its give detail about what that finding is. So yes, "that" refers to "finding".


Hi Shraddha/ E-Gmat,

"Certain pesticides can become ineffective if used repeatedly in the same place； one reason is suggested by the finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals．"

In this sentence, "that" refers to "finding" as its give detail about what that finding is. So yes, "that" refers to "finding".

Now I am bit confused that how that can modify "finding" ,1)Finding is singular subject but the verb used for that is "are" ( since that act as subject here) ,2) logically if I replace that with finding then the clause becomes "finding are free of such chemicals" and 3)how can that jump over a complete clause to modify finding.

Kindly advise me about the above , maybe my understanding of That is completely wrong.

Tks/Brgds
Anurag

Hi Anurag,

You ask a good question, and I am sure this question must have confused many of the test-takers. To understand what is happening in this sentence, let's begin with a very simple basic example:

My brother showed me the watch that he found near the lake that is just behind our house.

So here we have two "that". Let's talk about the second one first. It is very clear that the second "that" modifies the preceding noun entity "lake". In this usage, "that" acts a Subject for which the Verb is "is".

Now let's talk about the first "that". Here "that" is acting as a Relative Pronoun because it gives us more information about the preceding noun entity "the watch". However, "that" here is NOT the Subject of the clause that is starts. The Subject of the Dependent Clause started by "that" is "he" and the Verb for this Subject is "found". This usage is not as common on GMAT as the second usage of "that" is.

In the official sentence in question has the similar usage of "that".

Certain pesticides can become ineffective if used repeatedly in the same place; one reason is suggested by the finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals．

The "that" after "finding" refers back to "finding" only. Now study the following two examples to understand the SV pair in the DC started by this "that".

There is an apple on the table.
There are many fruits on the table.

Now, many would say that in both the sentences, "there" is the Subject. If that is so then why the first sentence uses Singular Verb "is" and the second sentence uses Plural Verb "are"? The reason for this is that the Subject in the first sentence is "an apple" - a Singular noun entity, and the Subject in the second sentence is "many fruits" - a Plural noun entity. "There" in both the sentences actually works as placeholders.

Sp again, in the official sentence, in the clause "there are much larger populations of pesticide-degrading microbes...", the Subject is Plural "much larger populations". This is the reason why the clause has the Plural Verb "are". "There" is just a placeholder here.

Hope this helps.
Thanks.
Shraddha
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(A) Certain pesticides can become ineffective if used repeatedly in the same place；one reason is suggested by the finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals．Correct - structure of sentence is okay; comparison "in soils with a relatively long history of pesticide use" + "are much larger populations of X" "than" "in soils that are free of such chemicals"

(B) If used repeatedly in the same place，one reason that certain pesticides can become ineffective is suggested by the finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals．Wrong - "if" clause is frequently used with "then" clause; "one reason...is suggested...by the finding that" is redundant.

(C) If used repeatedly in the same place，one reason certain pesticides can become ineffective is suggested by the finding that much larger populations of pesticide-degrading microbes are found in soils with a relatively long history of pesticide use than those that are free of such chemicals．Wrong - "if" clause is frequently used with "then" clause; "one reason...is suggested...by the finding that" is redundant; comparison clause of "in soils..." and "those that" is not structurally similar

(D) The finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals is suggestive of one reason，if used repeatedly in the same place，certain pesticides can become ineffective．Wrong - comma splice. You cannot combine two dependent clauses with a comma

(E) The finding of much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in those that are free of such chemicals suggests one reason certain pesticides can be come ineffective if used repeatedly in the same place. comparison clause of "in soils..." and "those that" is not structurally similar; "one reason certain pesticides" must have a conjunction or the sentence is not grammatical.

IMO A

Certain pesticides can become ineffective if used repeatedly in the same place；one reason is suggested by the finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals．


(A) Certain pesticides can become ineffective if used repeatedly in the same place；one reason is suggested by the finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals．

(B) If used repeatedly in the same place，one reason that certain pesticides can become ineffective is suggested by the finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals．

pesticides are used repeatedly not any reason. Modifier error.

(C) If used repeatedly in the same place，one reason certain pesticides can become ineffective is suggested by the finding that much larger populations of pesticide-degrading microbes are found in soils with a relatively long history of pesticide use than those that are free of such chemicals．

pesticides are used repeatedly not any reason. Modifier error. Also this implies that removal of that makes the sentence awkward.

(D) The finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals is suggestive of one reason, if used repeatedly in the same place, certain pesticides can become ineffective.

Suggestive of is not idiomatic and ambiguous
Also there is no proper conjunction between two clauses. comma does not help us get intended meaning.

(E) The finding of much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in those that are free of such chemicals suggests one reason certain pesticides can become ineffective if used repeatedly in the same place.

finding of microbes does not make sense.
that cannot refer to those and also not refer to soils properly.

Certain pesticides can become ineffective if used repeatedly in the same place；one reason is suggested by the finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals．


(A) Certain pesticides can become ineffective if used repeatedly in the same place; one reason is suggested by the finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals．
(B) If used repeatedly in the same place，one reason that certain pesticides can become ineffective is suggested by the finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals．
(C) If used repeatedly in the same place，one reason certain pesticides can become ineffective is suggested by the finding that much larger populations of pesticide-degrading microbes are found in soils with a relatively long history of pesticide use than those that are free of such chemicals．
(D) The finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals is suggestive of one reason, if used repeatedly in the same place, certain pesticides can become ineffective.
(E) The finding of much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in those that are free of such chemicals suggests one reason certain pesticides can become ineffective if used repeatedly in the same place.


The shortest way to tackle this horrendous topic is to eliminate some number of choices through modification. In B and C, you have an introductory modifier and what follows after comma must be certain pesticides. Hence eliminate choices B and C. The idiom suggestive of is not the correct idiom. In fact, the olden days, suggestive was used only in cases involving sexual connotations. Between A and E, the missing of the connector 'that' after -reason- in a reported speech is a phenomenal error in E. Therefore A.

Has OG ever repeated this topic in any further versions of OG10?

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Certain pesticides can become ineffective if used repeatedly in the same place；one reason is suggested by the finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals.

(A) Certain pesticides can become ineffective if used repeatedly in the same place；one reason is suggested by the finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals.
CORRECT

(B) If used repeatedly in the same place，one reason that certain pesticides can become ineffective is suggested by the finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals.
Incorrect since after comma the consequence (Pesticides become ineffective) of IF Clause should come.

(C) If used repeatedly in the same place，one reason certain pesticides can become ineffective is suggested by the finding that much larger populations of pesticide-degrading microbes are found in soils with a relatively long history of pesticide use than those that are free of such chemicals.
Incorrect since after comma the consequence (Pesticides become ineffective) of IF Clause should come. Moreover, lack of THAT after ONE REASON leads to a Fragmented sentence

(D) The finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals is suggestive of one reason, if used repeatedly in the same place, certain pesticides can become ineffective.
After removing modifiers, the sentence would be-
The finding is suggestive of one reason, if used repeatedly in the same place, certain pesticides can become ineffective.
A Run-on sentence. Hence Incorrect.

(E) The finding of much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in those that are free of such chemicals suggests one reason certain pesticides can become ineffective if used repeatedly in the same place.
After removing modifiers, the sentence would be-
The finding suggests one reason certain pesticides can become ineffective if used repeatedly in the same place,
Lack of THAT after ONE REASON leads to a Fragmented sentence. Hence Incorrect.