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# The industrial pollutants known as PCB`s were first

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Magoosh GMAT Instructor
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Re: The industrial pollutants known as PCB`s were first  [#permalink]

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27 Nov 2015, 12:32
EducationAisle wrote:
Hi Mike, thanks for your post.

So, are you suggesting that the usage of Past Perfect on GMAT would always be accompanied by indirect speech?

Also, curious to know why you say it's a confusing scenario.

Dear EducationAisle,
I'm happy to respond.

First of all, I wouldn't say that, on the GMAT, indirect speech always requires the Past Perfect Tense. The GMAT is quite nuanced on this point. If another feature of the sentence ("several years earlier," etc.) makes clear the time reference, then the GMAT may choose to forgo entirely the Past Perfect. It really depends on the subtleties of a case-by-case basis.

When the GMAT does use the Past Perfect in a non-indirect-speech scenario, it always follows the rule that the event furthest in the past, before the other past events, is in the past perfect. It's simply a by-product of the GMAT's conventions that the action in the past perfect is the earliest action in the entire sentence, the action furthest in the past. In that light, think about the sentence you proposed:
The industrial pollutants known as PCB's were first manufactured in 1929 and were used as coolants for electrical equipment in Europe and North America, but by 1970's, the compounds had entered the food chain and were harmful to some animals.
Now, think about the time-relationship of the verbs in that sentence. The most recent action, Action #1, was "were harmful," and the Action #2 "had entered" happened before this more recent action and appears in the past perfect. So far, so good. But then, we have two actions even further in the past: Action #3 "were first manufactured" and Action #4 "were used." Actions #3 & #4 happened before Action #2, but Action #2 is in the past perfect, and Actions #3 & #4 are not! We have one action in the past perfect, and two actions that happened before the event in the past perfect that are in the simple past tense. If we put these actions in historical sequence, we would get:
Deepest past --- Action #3 --- Action #4 --- Action #2 ---Action #1---Present Time
According to the GMAT convention, if we are going to use the past perfect for any verbs at all, then the action in the furthest past should be one of the verbs that has the past perfect. Admittedly, sometimes the GMAT relies on other indicators, such as the year dates in this sentence, to indicate sequence, but then the GMAT entirely forgoes the past perfect tense, and relies exclusively on these other indicators. What's confusing is using the past perfect for an event that is relatively more recent and not using it for the even furthest in the past. Even if this sentence is technically grammatically correct, it would not appear on the GMAT because the conventions are mixed and it would be thereby confusing to students.

Does all this make sense?
Mike
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Re: The industrial pollutants known as PCB`s were first  [#permalink]

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28 Nov 2015, 08:55
Hi Mike, thanks for your elaborate post.

mikemcgarry wrote:
First of all, I wouldn't say that, on the GMAT, indirect speech always requires the Past Perfect Tense. The GMAT is quite nuanced on this point. If another feature of the sentence ("several years earlier," etc.) makes clear the time reference, then the GMAT may choose to forgo entirely the Past Perfect. It really depends on the subtleties of a case-by-case basis.

My question was slightly different. I did not intend to ask whether indirect speech always requires the Past Perfect Tense. My question was the other way round: Does the the Past Perfect Tense always require an indirect speech. My answer is no and hence the reason I re-articulated this sentence removing the indirect speech showed that, while still retaining the past perfect.

Quote:
Admittedly, sometimes the GMAT relies on other indicators, such as the year dates in this sentence, to indicate sequence,

That’s exactly what’s happening here.

We have a specific year (1929), which clearly has to be in simple past. Note that this cannot be in Past Perfect, because Past Perfect (in fact, all perfect tenses for that matter) are associated with unspecified time. So, there is no confusion on the sequence of events, in the sentence that I have proposed:

i) PCB's were first manufactured in 1929 – Clearly this is the oldest event (the usage of first in this context makes it very clear)

ii) PCB's were used as coolants for electrical equipment in Europe and North America - clearly this could not have happened before PCB’s were manufactured

iii) by 1970's, the compounds had entered the food chain – Usage of past perfect is apt here, because it clearly indicates that this act of entering the food chain occurred sometime in or before 1970's, but the time frame (of entering the food chain) goes back only till 1929.

iv) by 1970's, the compounds were harmful to some animals – I think we have a common understanding on this one that the usage of Simple past is appropriate here.

Quote:
It's true that if the latter half stood as a sentence on its own, then the past perfect would be justified.

Grammatically, this latter half (by 1970's, the compounds had entered…..) actually is an Independent clause (as you would obviously know that coordinating conjunctions and semicolons connect two Independent clauses; here, but, a coordinating conjunction is used).

However, if you are suggesting that the rest of the sentence should not have appeared at all, then the sentence would have been:

By 1970's, the compounds had entered the food chain and were harmful to some animals.

The above sentence would mean that from eternity in the past, till 1970’s, the compounds had entered the food chain. However, clearly the intent of the sentence is to not go back from 1970’s to eternity, but to go back only till 1929. The first part of the sentence (by categorically mentioning 1929) serves as a reference to clearly indicate that the time frame of reference is not from eternity to 1970’s", but from 1929 to 1970’s.
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EducationAisle, Bangalore

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Re: The industrial pollutants known as PCB`s were first  [#permalink]

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10 Sep 2016, 11:14
Hello Mike,

Could you please explain the usage of past perfect in this sentence in the light of another OG question. His studies of ice-polished rocks in his Alpine home land, far outside the range of present-day glaciers, led Louis Agassiz in 1837 to propose the concept of an age in which great ice sheets had existed in now currently temperate areas.

In both the questions, some studies led to some results. However, in industrial pollutant question usage of past perfect is justified whereas in ice sheet question usage of past perfect is considered wrong. Why ? Please explain.

Thanks !
Magoosh GMAT Instructor
Joined: 28 Dec 2011
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Re: The industrial pollutants known as PCB`s were first  [#permalink]

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12 Sep 2016, 10:27
2
karant wrote:
Hello Mike,

Could you please explain the usage of past perfect in this sentence in the light of another OG question. His studies of ice-polished rocks in his Alpine home land, far outside the range of present-day glaciers, led Louis Agassiz in 1837 to propose the concept of an age in which great ice sheets had existed in now currently temperate areas.

In both the questions, some studies led to some results. However, in industrial pollutant question usage of past perfect is justified whereas in ice sheet question usage of past perfect is considered wrong. Why ? Please explain.

Thanks !

Dear karant,

I'm happy to respond. The first thing I will say is that student mistakenly believe that the SC GMAT is primarily a test of grammar. In fact, grammar is only one of three equally important strands---the other two are [urlhttp://magoosh.com/gmat/2013/logical-predication-on-the-gmat-sentence-correction/]logic[/url] and rhetoric. What you are asking here is not a matter of grammar: it's a matter of logic.

The simple rule is that GMAT considers the past perfect either questionable or outright wrong when its use is entirely redundant. The GMAT is 100% against redundancy. Therefore, we have to use logic to figure out what's redundant and what's not.

Look at this sentence, the SC question in this thread. This is (A), the OA:
The industrial pollutants known as PCB's were first manufactured in 1929 and were used as coolants for electrical equipment in Europe and North America until the 1970's, when studies showed that the compounds had entered the food chain and were harmful to some animals.
This version has the past perfect, and the use of the past perfect makes very clear that in the 1970s, when the studied were done, the pollution problem had taken place already. The environment was already contaminated by the time when scientists conducted these studies.

Now, change that to the simple past:
The industrial pollutants known as PCB's were first manufactured in 1929 and were used as coolants for electrical equipment in Europe and North America until the 1970's, when studies showed that the compounds entered the food chain and were harmful to some animals.
This changes the meaning. This tells us that no PCB's entered the food chain before the 1970's, but somehow, right when the studied were done, that's when the pollutants suddenly permeated the entire food chain. First of all, that's completely nonsense, but also that's a completely different meaning.

Therefore, the past perfect is required in that question, because removing the past perfect changes the meaning. If you can take something out and the meaning changes, then what you have taken out is not redundant. By definition, something is redundant only when it can be removed without altering the meaning in the least. Once again, the GMAT is 100% against redundancy.

Now, look at that OG SC problem, #89 in the OG 2017. Incidentally, my friend, it is common courtesy to cite the exact number of any question you quote from the OG.

Here's (A), with the past perfect.
His studies of ice-polished rocks in his Alpine home land, far outside the range of present-day glaciers, led Louis Agassiz in 1837 to propose the concept of an age in which great ice sheets had existed in now currently temperate areas.
Let's just keep this same version, but change the past perfect to the simple past:
His studies of ice-polished rocks in his Alpine home land, far outside the range of present-day glaciers, led Louis Agassiz in 1837 to propose the concept of an age in which great ice sheets existed in now currently temperate areas.
Absolutely no change in meaning. Louis Agassiz was doing this work in 1837, and both versions make very clear that the "age" of the "great ice sheets" was well before 1837--in fact, it was back in the most recent Ice Age. Whether we have the past perfect or the simple past, the sentence has exactly the same meaning: by definition, that makes the use of the past perfect tense redundant in this context.

You see, my friend, there is no simple rule about when the past perfect is right or wrong. You have to think about the logic of the situation and ask yourself whether the meaning changes if you change the past perfect to the simple past. Any feature of a sentence that can be removed without changing the meaning is, by definition, redundant.

Does all this make sense?
Mike
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Education is not the filling of a pail, but the lighting of a fire. — William Butler Yeats (1865 – 1939)

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Re: The industrial pollutants known as PCB`s were first  [#permalink]

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12 Sep 2016, 11:22
mikemcgarry wrote:
karant wrote:
Hello Mike,

Could you please explain the usage of past perfect in this sentence in the light of another OG question. His studies of ice-polished rocks in his Alpine home land, far outside the range of present-day glaciers, led Louis Agassiz in 1837 to propose the concept of an age in which great ice sheets had existed in now currently temperate areas.

In both the questions, some studies led to some results. However, in industrial pollutant question usage of past perfect is justified whereas in ice sheet question usage of past perfect is considered wrong. Why ? Please explain.

Thanks !

Dear karant,

I'm happy to respond. The first thing I will say is that student mistakenly believe that the SC GMAT is primarily a test of grammar. In fact, grammar is only one of three equally important strands---the other two are [urlhttp://magoosh.com/gmat/2013/logical-predication-on-the-gmat-sentence-correction/]logic[/url] and rhetoric. What you are asking here is not a matter of grammar: it's a matter of logic.

The simple rule is that GMAT considers the past perfect either questionable or outright wrong when its use is entirely redundant. The GMAT is 100% against redundancy. Therefore, we have to use logic to figure out what's redundant and what's not.

Look at this sentence, the SC question in this thread. This is (A), the OA:
The industrial pollutants known as PCB's were first manufactured in 1929 and were used as coolants for electrical equipment in Europe and North America until the 1970's, when studies showed that the compounds had entered the food chain and were harmful to some animals.
This version has the past perfect, and the use of the past perfect makes very clear that in the 1970s, when the studied were done, the pollution problem had taken place already. The environment was already contaminated by the time when scientists conducted these studies.

Now, change that to the simple past:
The industrial pollutants known as PCB's were first manufactured in 1929 and were used as coolants for electrical equipment in Europe and North America until the 1970's, when studies showed that the compounds entered the food chain and were harmful to some animals.
This changes the meaning. This tells us that no PCB's entered the food chain before the 1970's, but somehow, right when the studied were done, that's when the pollutants suddenly permeated the entire food chain. First of all, that's completely nonsense, but also that's a completely different meaning.

Therefore, the past perfect is required in that question, because removing the past perfect changes the meaning. If you can take something out and the meaning changes, then what you have taken out is not redundant. By definition, something is redundant only when it can be removed without altering the meaning in the least. Once again, the GMAT is 100% against redundancy.

Now, look at that OG SC problem, #89 in the OG 2017. Incidentally, my friend, it is common courtesy to cite the exact number of any question you quote from the OG.

Here's (A), with the past perfect.
His studies of ice-polished rocks in his Alpine home land, far outside the range of present-day glaciers, led Louis Agassiz in 1837 to propose the concept of an age in which great ice sheets had existed in now currently temperate areas.
Let's just keep this same version, but change the past perfect to the simple past:
His studies of ice-polished rocks in his Alpine home land, far outside the range of present-day glaciers, led Louis Agassiz in 1837 to propose the concept of an age in which great ice sheets existed in now currently temperate areas.
Absolutely no change in meaning. Louis Agassiz was doing this work in 1837, and both versions make very clear that the "age" of the "great ice sheets" was well before 1837--in fact, it was back in the most recent Ice Age. Whether we have the past perfect or the simple past, the sentence has exactly the same meaning: by definition, that makes the use of the past perfect tense redundant in this context.

You see, my friend, there is no simple rule about when the past perfect is right or wrong. You have to think about the logic of the situation and ask yourself whether the meaning changes if you change the past perfect to the simple past. Any feature of a sentence that can be removed without changing the meaning is, by definition, redundant.

Does all this make sense?
Mike

Thanks Mike for the detailed response !

The industrial pollutants known as PCB's were first manufactured in 1929 and were used as coolants for electrical equipment in Europe and North America until the 1970's, when studies showed that the compounds had entered the food chain and were harmful to some animals.

The wording of the sentence is such that if we remove past perfect tense from the sentence, it wrongly suggests the co-relation between studies showed and compounds entered into the food chain.

His studies of ice-polished rocks in his Alpine home land, far outside the range of present-day glaciers, led Louis Agassiz in 1837 to propose the concept of an age in which great ice sheets existed in now currently temperate areas.

However, in the above sentence, the wording his studies ...led Louis Agassiz suggests that the studies and the concept of an age are two separate events. Hence, sequencing of events is already clear and does not require past perfect tense.

Am I correct in my understanding ?

It does making sense to me now. However, it can be little tough to find out these differences in timed condition.

Thanks !
Magoosh GMAT Instructor
Joined: 28 Dec 2011
Posts: 4486
Re: The industrial pollutants known as PCB`s were first  [#permalink]

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14 Sep 2016, 09:45
karant wrote:
Thanks Mike for the detailed response !

The industrial pollutants known as PCB's were first manufactured in 1929 and were used as coolants for electrical equipment in Europe and North America until the 1970's, when studies showed that the compounds had entered the food chain and were harmful to some animals.

The wording of the sentence is such that if we remove past perfect tense from the sentence, it wrongly suggests the co-relation between studies showed and compounds entered into the food chain.

His studies of ice-polished rocks in his Alpine home land, far outside the range of present-day glaciers, led Louis Agassiz in 1837 to propose the concept of an age in which great ice sheets existed in now currently temperate areas.

However, in the above sentence, the wording his studies ...led Louis Agassiz suggests that the studies and the concept of an age are two separate events. Hence, sequencing of events is already clear and does not require past perfect tense.

Am I correct in my understanding ?

It does making sense to me now. However, it can be little tough to find out these differences in timed condition.

Thanks !

Dear karant,
I'm happy to respond.

My friend, you are quite correct in your understanding. The way to improve speed is through a habit of reading. See this blog:
How to Improve Your GMAT Verbal Score
When you make a habit of reading sophisticated material, extracting the subtle meaning from difficult passages repeatedly, then the GMAT SC won't seem nearly as hard. To get good at words, you have to dive into words.

Does all this make sense?
Mike
_________________

Mike McGarry
Magoosh Test Prep

Education is not the filling of a pail, but the lighting of a fire. — William Butler Yeats (1865 – 1939)

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Re: The industrial pollutants known as PCB`s were first  [#permalink]

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14 Sep 2016, 11:16
Mike, your explanations to SC are always crisp and easy to understand

mikemcgarry wrote:
mun23 wrote:
The industrial pollutants known as PCB's were first manufactured in 1929 and were used as coolants for electrical equipment in Europe and North America until the 1970's,when studies showed that the compounds had entered the food chain and were harmful to some animals.

(A) that the compounds had entered the food chain and were harmful to some animals.
(B) the compounds to have entered the food chain and be harmful to some animals
(C) the entry of the compounds into the food chain as harmful to some animals
(D) the entry of the compounds into the food chain and its harmfulness to animals
(E) the compounds entering into the food and harming some animals

Dear mun23,

Idiomatically, the verb "show" (like the verbs "think", "tell", "know", "believe" and a host of other "cognitive" verbs) must take a "that"-clause.
show that P does Q
The word "that" is omitted in colloquial, informal English, but it's absolutely needed on the GMAT. The only choice that does this correctly is (A).
We can't use the infinitive structure
show P to do Q
This is the mistake of (B).
The other choices have a variety of idiomatically incorrect options --- participles, "P as Q", etc. The verb "show" demands a "that"-clause.

Does this make sense?

Mike
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Re: The industrial pollutants known as PCB`s were first  [#permalink]

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15 Sep 2016, 10:57
mikemcgarry wrote:
karant wrote:
Thanks Mike for the detailed response !

The industrial pollutants known as PCB's were first manufactured in 1929 and were used as coolants for electrical equipment in Europe and North America until the 1970's, when studies showed that the compounds had entered the food chain and were harmful to some animals.

The wording of the sentence is such that if we remove past perfect tense from the sentence, it wrongly suggests the co-relation between studies showed and compounds entered into the food chain.

His studies of ice-polished rocks in his Alpine home land, far outside the range of present-day glaciers, led Louis Agassiz in 1837 to propose the concept of an age in which great ice sheets existed in now currently temperate areas.

However, in the above sentence, the wording his studies ...led Louis Agassiz suggests that the studies and the concept of an age are two separate events. Hence, sequencing of events is already clear and does not require past perfect tense.

Am I correct in my understanding ?

It does making sense to me now. However, it can be little tough to find out these differences in timed condition.

Thanks !

Dear karant,
I'm happy to respond.

My friend, you are quite correct in your understanding. The way to improve speed is through a habit of reading. See this blog:
How to Improve Your GMAT Verbal Score
When you make a habit of reading sophisticated material, extracting the subtle meaning from difficult passages repeatedly, then the GMAT SC won't seem nearly as hard. To get good at words, you have to dive into words.

Does all this make sense?
Mike

Thank you Mike for the guidance!

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Re: The industrial pollutants known as PCB`s were first  [#permalink]

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18 Oct 2016, 09:40
Nevernevergiveup

When one verb occurs within a statement then the tense of the verb is expressed from the perspective of the time when the statement is made. Following are the various cases:
Future from the perspective of past:

I SAID that I WOULD COME. (Coming happens in future of saying - future of past is expressed by conditional tense WOULD)
Past from perspective of past:
I SAID that I HAD SEEN him. ( Seeing happens in past of saying - past of past is expressed by past perfect)

Future from the perspective of present:
I say that I will come. (Future of present is future)
I say that I saw him. (Past of present is past)

In short, remember that when using a statement in past, take all the verbs within the statement one tense backward. i.e., future will becomes conditional would and past becomes past perfect.
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Re: The industrial pollutants known as PCBs were first manufactured  [#permalink]

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01 Jan 2017, 07:46
I know other errors in C.
But what's wrong with structure show X as y in general?
According to official explanation, structure here should be show X to be y.
This show x as y error comes often in official questions.
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The industrial pollutants known as PCBs were first manufactured  [#permalink]

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01 Jan 2017, 10:24
rulez161 wrote:
I know other errors in C.
But what's wrong with structure show X as y in general?
According to official explanation, structure here should be show X to be y.
This show x as y error comes often in official questions.

This is an idiomatic usage. For idioms, one needs to memorize the correct usages - there are in general no explanations for such usages.
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Re: The industrial pollutants known as PCB`s were first  [#permalink]

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19 Dec 2017, 13:27
Merged topics. Please, search before posting questions!
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Re: The industrial pollutants known as PCB`s were first   [#permalink] 19 Dec 2017, 13:27

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