Around 1900, fishermen in the Chesapeake Bay area landed more than

Yes, while daagh has already explained it with an official example, another GMATPrep sentence that comes to mind:

In 1981 children in the United States spent an average of slightly less than two and a half hours a week doing household chores; by 1997 that figure had grown to nearly
six hours a week.

There are actually 3 events that this sentence talks about:

(a) children in the United States spent an average of slightly less than two and a half hours a week doing household chores (1981)

(b) 16 years passing since then (between 1981 and 1997)

(c) But, before those 16 years passed (within those years, as indicated by the words by 1997), that figure (two and a half hours a week doing household chores) went up to 6 hours.

However, while (b) and (c) both happened in the past, (c) happened before (b) and hence, (c) should be in past perfect (in this case: had grown). In fact, this is a classical usage of Past Perfect.

Our book EducationAisle Sentence Correction Nirvana discusses this concept of Past perfect tense, its application and examples in significant detail. In the book, we have provided a similar example:

In 2007, a typical web user spent less than 4 hours a month on Facebook; by 2011, that figure had gone up to 8 hours.

If someone is interested, PM me your email-id, I can mail the corresponding section of the book.

The first decision point is "that" vs "having." When we're using a modifier to specify a noun, or differentiate that noun from a larger group, we'd use "that." For example:

"The dog that ate Dana's homework is kind of a jerk."

In this case, there could be multiple dogs, and I'm differentiating between the dog that ate Dana's homework and other dogs with better etiquette.

I'm not sure there's ever a time when "having" would be mandatory, but if we were to use it as a modifier, we'd do so to add incidental information:

"The dog, having eaten Dana's homework, is no longer hungry."

Notice that in this case, "having eaten Dana's homework" is set off by commas to communicate that this information isn't crucial. There's only one dog, and this dog happened to have eaten Dana's homework. (Notice also that the phrase beginning with "having + verb" describes an action that happened before the other action in the sentence.)

In this question, we're talking specifically about the "milldams sand culverts that blocked shad" as opposed to milldams and culverts, in general. And while comma usage is rarely important, notice also that "having" isn't set off by commas. Therefore we'd prefer "that" to "having." That's one reason to pick (B).

A second decision point is the verb tense, "had reduced" vs. "reduced." Any time we have the construction "By + YEAR IN PAST," and we wish to communicate that the action in question happened before this year, we'd use "had." In this case, the sentence includes the phrase "by 1920," and the reduction seems to have happened before 1920, so "had reduced" is correct, and (B) is again our champion.

I hope that helps!

Hello monidip1010,

I will be glad to help you out with this one.


This official sentence uses the phrase by 1920. Whenever the phrase by 1234 is used in a sentence, it requires the usage of past perfect tense. It is so because the expression denotes that first some other action took place, and then 1234 arrived.

Same is the case with the usage of by 1920 in this official sentence. Presence of this phrase says that over-fishing and the proliferation of milldams and culverts had already reduced the amount of landings by the time 1920 arrived. Hence, use of past perfect tense verb had reduced is correct.


Hope this helps.
Thanks.
Shraddha

SamulWitwicky
Hi

Point 1.
We are guided by a similar official example from GMATPREP as given below , which has given us the clue why such structures are accepted by GMAT. This is really different from normal thinking and we have to accept it as such.

After seeing that, please go through the explanation by Ron, one of the most noted personalities of GMAT SC in the link given
https://www.manhattanprep.com/gmat/foru ... t1864.html

Point 2.


For an understanding of the of the sequence, you may need to know a little bit about the life-cycle of the shad. Adult shads are sea –living; but the young ones cannot tolerate sea water. So the adults reach the seashores and then swim up the rivers that join the bay from the land. After travelling a good length, they spawn in fresh waters; they adults may either die away immediately after spawning or may return to the sea to pick up strength and re-enter rivers for spawning again.

The young ones then hatch in the river waters and stay there for six months or so, before they return to the sea via the same sea shore from where the mother entered the river. Now overfishing can occur in the following areas. 1. of the adults at the sea-shore area before entering the rivers. 2. in the rivers while they swim up for spawning, or when the growing young ones are trying to return to the sea. Meantime the inland guys are building dams and culverts for agriculture and energy production.The building of dams and culverts blocks the free flow of water as well as the swim of both the adults upstream and the young ones downstream. The young ones, if they do not reach seawaters with in a given time, will die out. The point is that all the impediments progressively have brought down the population of fish in the bay area, in a span of 20 years from 17mn in 1900 to barely 4 mn in 1920. Landings here imply the overall population.

Samuel! This is as far as I know of this episode from my readings. I may be wrong too.

Dear Friends,

Here is a detailed explanation to this question-
Concepts tested here: Tenses + Verb Forms + Pronouns + Awkwardness/Redundancy

A: This answer choice incorrectly uses the present perfect tense verb "have blocked" to refer to an action that concluded in the past; please remember, the simple past tense is used to refer to events that concluded in the past, and the present perfect tense (marked by the use of the helping verb “has/have”) is used to describe events that concluded in the past but continue to affect the present. Further, Option A suffers from pronoun ambiguity, as the pronoun "their" lacks a logical referent. Additionally, Option A uses the needlessly indirect phrase "shad migrations up their spawning streams", leading to awkwardness.

B: Correct. This answer choice correctly uses the simple past tense verb "blocked" to refer to an action that concluded in the past. Further, Option B correctly uses the past perfect tense verb "had reduced" to refer to the earlier of two actions that concluded in the past - over-fishing and the proliferation of milldams and culverts reducing landings and the year 1920 beginning. Additionally, Option B avoids the pronoun error seen in Options A and E, as it provides an appropriate referent - "shad" - for the pronoun "their". Besides, Option B is free of any awkwardness or redundancy.

C: This answer choice incorrectly uses the simple past tense verb "reduced" to refer to the earlier of two actions that concluded in the past - over-fishing and the proliferation of milldams and culverts reducing landings and the year 1920 beginning; please remember, the past perfect tense (marked by the use of helping verb "had") is used when a sentence contains two actions in the past; the helping verb "had" is used with the action in the "greater past", and the simple past tense is used to refer to events that concluded in the past. Further, Option C uses the needlessly wordy phrase "to a lower amount", leading to awkwardness and redundancy.

D: This answer choice incorrectly uses the past perfect participle phrase "having blocked" to refer to an action that concluded in the past; please remember, the simple past tense is used to refer to events that concluded in the past. Further, Option D incorrectly uses the simple past tense verb "reduced" to refer to the earlier of two actions that concluded in the past - over-fishing and the proliferation of milldams and culverts reducing landings and the year 1920 beginning; please remember, the past perfect tense (marked by the use of helping verb "had") is used when a sentence contains two actions in the past; the helping verb "had" is used with the action in the "greater past", and the simple past tense is used to refer to events that concluded in the past.

E: This answer choice incorrectly uses the past perfect participle phrase "having blocked" to refer to an action that concluded in the past; please remember, the simple past tense is used to refer to events that concluded in the past. Further, Option E suffers from pronoun ambiguity, as the pronoun "their" lacks a logical referent. Additionally, Option E uses the needlessly indirect phrases "shad migrations up their spawning streams" and "to an amount lower", leading to awkwardness.

Hence, B is the best answer choice.

To understand the concept of "Simple Tenses" on GMAT, you may want to watch the following video (~1 minute):



To understand the concept of "Past Perfect Tense" on GMAT, you may want to watch the following video (~2 minutes):



To understand the concept of "Present Perfect Tense" on GMAT, you may want to watch the following video (~1 minute):



All the best!
Experts' Global Team

B. Around 1900, fishermen in the Chesapeake Bay area landed more than seventeen million pounds of shad in a single year, but by 1920, over-fishing and the proliferation of mill dams and culverts that blocked shad from migrating up their spawning streams had reduced landings to less than four million pounds.

Around 1900, fishermen in the Chesapeake Bay area landed more than seventeen million pounds of shadin a single year, but by 1920, over-fishing and the proliferation of mill dams and culverts that blocked shad from migrating up their spawning streams had reduced landings to less than four million pounds.

fishermen in the Chesapeake Bay area landed more than seventeen million pounds of shad, over-fishing and the proliferation of mill dams and culverts had reduced landings to less than four million pounds.


How can the answer be 'B' ?

Doesn't use of Past perfect in B show that 'Reduced landings' is happening before 'Fisherman landed more than 17m pound' ?

Hi dinesh86,

as per the sentence construction it is obvious that "landing more than seventeen million pounds of shad in a single year" happened prior to the events in 1920 so there is no need to include that in the timeline.

As per B, "that" is rightly used to refer to what caused the blockage that is:"over-fishing and the proliferation of milldams and culverts" and the option follows a cause and effect relationship. so as per the timeline.. "had reduced" is correct..

In D and E.. having (verb-ing modifier) wrongly modifies" the milldams and culverts".

Regards,
Dom.

Daagh, I really need your help on this one. My GMAT centre tells me that for 2 sequential events, the 1st event is in past perfect, and the second in simple past. The example it gave is: "He had never seen (1st event) a GMAT question before he actually took (later event) the exam".

Next question, I still don't understand the sequence of events happening here. Is it: 17mill landings --> some guys build stuff --> these stuff block shad migration + they guys overfish --> therefore landings are reduced??

Do hope you see this, this question is driving me nuts lol

Hey thanks a lot Daagh. And thanks a lot for the link. Took me awhile to get it, but I think I do now. It's hard to put my thoughts into words but i'll try. So basically, this fisherman question, like the honeybee question, is merely stating facts ("narration" as Ron called it) - that at 1900, this was the scenario, then fastforward 20 years later, 1st event (i.e. overfishing +building) happened and resulted in another scenario. Same for the honeybee, after their release, then the first event (i.e. migration) happened. Therefore, this is the exception to the past perfect>>past tense rule.

VS

2 explicit actions for e.g. this question on buildings and earthquakes --> 37-og-vr-some-buildings-that-were-destroyed-and-heavily-56040.html

buildings had to be FIRST constructed badly, then SECOND, be destroyed by an earthquake. This is where the rule is essential in demonstrating the sequence of events.

what do you think of my reasoning?

In over-fishing and the proliferation of milldams and culverts that blocked shad migration
That refers to the preceding noun (culverts here), but it is not the culverts that blocked shad migration.
'over fishing and proliferation ' overall had an effect that blocked the migration. So ing+verb should be used to refer to the effect of the preceding statement.

Please correct me in this concept.

Hi ishajindal,

I hope my explanation will be of help to you.

Around 1900, fishermen in the Chesapeake Bay area landed more than seventeen million pounds of shad in a single year, but by 1920, over-fishing and the proliferation of milldams and culverts that have blocked shad migrations up their spawning streams had reduced landings to less than four million pounds.

(A) that have blocked shad migrations up their spawning streams had reduced landings to less
(B) that blocked shad from migrating up their spawning streams had reduced landings to less
(C) that blocked shad from migrating up their spawning streams reduced landings to a lower amount
(D) having blocked shad from migrating up their spawning streams reduced landings to less
(E) having blocked shad migrations up their spawning streams had reduced landings to an amount lower

Around 1900, fishermen in the Chesapeake Bay area landed more than seventeen million pounds of shad in a single year is a complete sentence by itself.

Looking at the next sentence, we realize that the contrast is mentioned. The sentence says that by year 1920, over-fishing and the proliferation of mill dams and culverts landings were already reduced to less than four million pounds. And, milldams and culverts blocked shad migrations up their spawning streams.

To answer your question,-ing form preceded by ',' shows results or additional information. But, -ing form not preceded by ',' modifies the closest noun. That is why choice D and E are wrong.

(A) that have blocked shad migrations up their spawning streams had reduced landings to less. 'have' represents past particple, but the event ended in past. Hence, past participle is not required.
(B) that blocked shad from migrating up their spawning streams had reduced landings to less. Correct option. 'had' is correctly used to show that the even happened already before 1920
(C) that blocked shad from migrating up their spawning streams reduced landings to a lower amount. 'lower amount' is not right.

"Having + past participle" is called a perfect participle - it is used to depict an action that has been completed.

Having done my homework, I went out to play.

===============

Post your query in the thread as usual and then click on the "request expert reply" button.

I understand why the past perfect "had reduced" is correct here - but how can the simple past tense "blocked" in the relative clause be correct? Doesn't this imply that the sequence of events is: "landings are reduced" followed by "the culverts blocked shad migrations"? But how is this logical? First the migrations are blocked by the culverts and subsequently (or perhaps at the same time) landings are reduced, so the verb tense for "blocked" should either be the same as "reduced" or further in the past then "reduced". Shouldn't the correct use of verb tenses be:
"...the proliferation of milldams and culverts that HAD BLOCKED shad migrations up their spawning streams HAD REDUCED landings to less than four million pounds"

?

The sequential relation is required to be established between the time reference 1920 and the verb "had reduced". The verb "blocked" is not a part of this relationship - hence past perfect is not to be used for this verb.

Hi natley4788, that would not be a great construct. Normally, past perfect is used to depict chronological sequence of two events/instances that happened one after the other in the past. Here however, clearly milldams and culverts were still there in 1920. So, at the very least, had blocked would make the sequence quite cryptic to understand.

That would be incorrect because the entire sentence talks about events/instances that happened in the past. So, we cannot be using present tense.

How is B the right answer??? It uses Past Perfect tense for an event that is happening later in the timeline. Pls help.

Around 1900, fishermen in the Chesapeake Bay area landed more than seventeen million pounds of shad in a single year, but by 1920, overfishing and the proliferation of milldams and culverts that have blocked shad migrations up their spawning streams had reduced landings to less than four million pounds.

=> Why " less than" but not " fewer than", as pounds is countable.
Hope someone could help
Thanks