Fifty years ago ecologists studying wolf recolonization down from

Question

Project SC Butler: Sentence Correction (SC1) 
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Fifty years ago, ecologists studying wolf recolonization down from Canada into Washington State hypothesized that  by killing coyotes, wolves will reverse the mesopredator overpopulation occurring when wolves were  eliminated from this region nearly a century earlier.

A) by killing coyotes, wolves will reverse the mesopredator overpopulation occurring when wolves were

B) by killing coyotes, wolves would reverse the mesopredator overpopulation that occurred when wolves were

C) by killing coyotes, wolves would reverse the mesopredator overpopulation that had occurred when wolves had been

D) wolves, by killing coyotes, will reverse the mesopredator overpopulation that had occurred when wolves were

E) wolves would, by killing coyotes, reverse the mesopredator overpopulation that occurred when wolves had been

THIS TOPIC IS TEMPORARILY LOCKED

generis · Answer

OFFICIAL EXPLANATION

Project SC Butler: Sentence Correction (SC1)

THE PROMPT  
 
→ Scientists hypothesized something in the past. The elimination of wolves and the mesopredator overpopulation  both  took place before this hypothesis. 
The easiest way to make that fact about both prior events clear is to use past perfect for both.

→ Because the first part of the sentence is in the simple past tense, the correct word to refer to the future (in the past) is  would  and not  will.

THE OPTIONS

→ The use of  will  to refer to a future event in the past is incorrect. Use  would  instead.
→ The phrase  wolves were  should be  wolves had been:  the wolf elimination took place before the hypothesis, which is the latest event in time and is described by the simple past tense.
→ The word  occurring  should probably be  that had occurred .
As this option stands, it erroneously intimates that the overpopulation   occurring when wolves were eliminated  .
ELIMINATE A

→ The elimination of wolves and the mesopredator overpopulation both took place before the hypothesis and hence probably require the past perfect tense  had occurred  and  had been eliminated . See my extra notes and Notes, below.
→ If you are not sure, keep B and compare to C (after you eliminate the last two).
ELIMINATE B

→ Correct. 
→ This sentence correctly uses  would  to refer to a future event in the past. 
→ It also uses the past perfect tense to describe the   two   earlier events.
KEEP

→ The use of  will  to refer to a future event in the past is incorrect. 
→ The phrase  wolves were  should be  wolves had been  because this wolf elimination took place before the hypothesis.

→ Bizarre verb tenses for the timeline.
In this option, the  earliest  event is written in simple past tense whereas the second-in-time event (mesopredator overpopulation) is written in past perfect!
ELIMINATE D

→ The mesopredator overpopulation took place before the hypothesis and thus requires the past perfect tense  had occurred. 
→ The style is a bit strange. True, short phrases such as  by killing coyotes  can be placed between auxililary (would) and main verb (reverse). But the other options do not "stick" this phrase in the middle of the verb construction.
 
ELIMINATE E

The best answer is C.

Another strategy

Split #1 :  would  is correct but  will  is not

Eliminate options A and D for using  will. 
When we talk about the "future in the past," we use  X  would  happen .

Split #2 : Compare the timelines of B, C, and E. 
Choose the option whose verbs are designed to convey the timeline—not that just happen to do so if you can keep track of the time markers.

Option B:

A) wolves  were eliminated  a century before the ecologists hypothesized = wolves were eliminated 150 years ago 
B) mesopredator overpopulation  occurred  = at some point in time . . . close to when wolves were eliminated?
C) ecologists  hypothesized  = 50 years ago
→ This option does not look terrible, but it seems odd that event B gets simple past tense because mesopredator overpopulation occurred after 150 years ago but before 50 years ago.
In other words, the mesopredator overpopulation comes  before  the hypothesis set down 50 years ago.
How do we best signal this pre-hypothesis timing of the mesopredator overpopulation?
We use  had occurred  to make it clear that overpopulation preceded the scientists' hypothesis.
After we think about this sentence for awhile, that fact seems obvious, but upon first reading, tracking on the timeline is hard. Make it easy.

Option C: 
A) wolves  had been  eliminated a century earlier = wolves had been eliminated 150 years ago, before the mesopredator overpopulation and before the hypothesis
B) mesopredator overpopulation  had occurred  at some time in the past after the wolves had been eliminated but before the ecologists hypothesized
C) ecologists hypothesized 50 years ago
→ This option seems better than B. 
Past perfect verb tense is used to describe "past of the past" events such as A and B here, both of which occurred before the hypothesis.
Can past perfect be used for two or more events in the past of the past that did  not  occur at the same time? Of course!
 The immigrant children were exhausted because they had traveled for weeks, been without enough food or water, and not slept for nearly two days.

Option E:
A) wolves  had been  eliminated= sometime  before  the hypothesis and before the mesopredator overpopulation
B) mesopredator overpopulation  occurred  = when? contemporaneously with the scientists hypothesis? No.
Mesopredator overpopulation is in the past of the past. 
C) ecologists  hypothesized

Compare these three.
Which one uses the verbs most efficiently or in a way that is most true to their purpose?

Option E is the worst of the lot because it contains a mixed or garbled message: two past of the past events, but one is described by one tense and the other, by another tense.
Eliminate E.

Now, Option B or C?
Err on the side of clarity. 
Using past perfect tense with sequence words is okay when the sequence words are not terribly clear and the sentence is dense.

Pick option C.

NOTES

• Sequence of events

A) 150 years ago: wolves were eliminated from Washington State

Sometime after #1 but BEFORE 50 years ago:

B) the population of mesopredators, including coyotes, grew too large

C) 50 years ago: ecologists were studying (contemplating) wolf recolonization.
The ecologists explored the idea of moving wolves from Canada down to Washington State 
→ notice: "ecologists   studying   wolf recolonization"

D) 50 years ago: ecologists hypothesized that bringing wolves from Canada to Washington state would reverse the problem of mesopredator overpopulation.
The ecologists hypothesized that this reversal would occur because wolves would kill coyotes. Apparently, coyotes constituted many or maybe all of the mesopredators whose population had grown too much.

Events C and D happened pretty much simultaneously. Both events are described in the nonunderlined portion of the sentence.
 Ecologists studying  is a reduced relative clause.
Relative clause:  ecologists who were studying    wolf recolonization
Reduced relative clause:  ecologists studying    wolf recolonization

Two events occurred  before  the ecologists hypothesized.
I described those two events and labeled them "A" and "B," respectively.

We use past perfect to talk about events in the past that happened before a different, more recent event in the past.

Events A and B happened at different times.
A century and a half ago, wolves were removed from Washington.
Then the mesopredator (coyote) population exploded.

Can we use past perfect for two or more events that occurred at different times but before a clearly later-in-time event? 
Absolutely yes. In fact, when timing or sequence is unclear or dense, we should do so.

Do sequence words mean that past perfect is unnecessary or optional and that we should rely only on simple past tense?
No. 
In  simple  sentences in which sequence is very simple, very clear, and signified by words such as  before, after, previously,  and  subsequently,  you probably do not need to use past perfect.

Is it incorrect to use past perfect with sequence words? No. 
The construction may not be ideal in sentences in which the time sequence is very clear, but it is not wrong.

A decade ago, such a sentence would not necessarily have been wrong, but would not likely have been the best answer.
Things have changed a bit.
I noted in a recent post that official questions in the last few years have contained both sequence words and past perfect.
In those official questions, despite the presence of a sequence word, I suspect that past perfect is used because the timeline is still hard to follow. 
Such is the case in this question.

So you think like a test maker.
Aspirant to self:  Self, this question tests verb tenses that describe events that occurred in the past.
Some of the events happened a long time before the other events.

This timing of events in this sentence is not very clear. I've read this thing three times and I finally figured out the timing.
Aha! If timing is difficult to discern even though time markers have been given, I should go with the verb tense that is designed to describe the earlier-in-time past events: past perfect . . . . the past of the past. 
 
  COMMENTS

Zain92  ,  PyjamaScientist  (what a great username) ,  kantapong  ,  dinubisht003  , and  Ratisbon1993  , welcome to SC Butler.

nehasheela2  ,  Shaajiib  , welcome to SC Butler, and I addressed your questions in my OE.

piyushluniya  , the presence of sequence words does not necessarily make the use of past perfect "optional," though I've given you kudos because your question goes right to the heart of the matter and I appreciate your politeness.

zanto  , you asked about the phrase "by killing coyotes."
On occasion, if we want to emphasize something in a short phrase, we can "split the verb" and insert the phrase.
To learn more about splitting the verb with a short phrase,  , see my post by clicking  here .

I honestly do not know whether GMAC would pit these two constructions against each other but believe a good chance of its writers doing so exists.

I am going to lock the topic for now.
I think it forces you to get outside rules that are by no means set in stone and to think about which verb most clearly expresses the chain of events in this complicated situation.

I may archive the question. I need to think about the matter.

Anyone who attempted this question gets kudos.
I respect bravery.

Stay safe.

Zain92 · Answer

A) by killing coyotes, wolves will reverse the mesopredator overpopulation occurring when wolves were
the researchers hypothesis was made in the past. Hence the use of "will" is incorrect
B) by killing coyotes, wolves would reverse the mesopredator overpopulation that occurred when wolves were
elimination of wolves should take past perfect.

C) by killing coyotes, wolves would reverse the mesopredator overpopulation that had occurred when wolves had been
Overpopulation occurred after the wolves had been eliminated. So there is no need to use past perfect with overpopulation. Rather elimination of wolves should take past perfect.

D) wolves, by killing coyotes, will reverse the mesopredator overpopulation that had occurred when wolves were
same as A.
E) wolves would, by killing coyotes, reverse the mesopredator overpopulation that occurred when wolves had been
CORRECT

Aswin12 · Answer

Option C is the correct answer. The act of hypothesizing by the scientist the related action in given in simple past tense.

PyjamaScientist · Answer

Fifty years ago, ecologists studying wolf recolonization down from Canada into Washington State hypothesized that  by killing coyotes, wolves will reverse the mesopredator overpopulation occurring when wolves were  eliminated from this region nearly a century earlier.

Timeline of events as per the stimulus. Wolves eliminated -> Mesopredator overpopulation occurs -> Ecologists (50 years back) hypothesise -> wolves will kill the coyotes and reverse the phenomenon

By creating a timeline of events in your head, it helps in determining the correct tense usage. So, let's see which answer choices use the best tenses and convey the intended meaning.

A) by killing coyotes, wolves will reverse the mesopredator overpopulation occurring when wolves were
 Ecologists hypothesised (past tense), correct tense to be used while expressing future from past- "would" not will

B) by killing coyotes, wolves would reverse the mesopredator overpopulation that occurred when wolves were
 This answer choice is close by not perfect. By using simple past tense "when wolves were" it doesn't convey the correct timeline. It makes it seem that the coyote's overpopulation and the elimination of wolves were two simultaneous events. Eg: He cooked the meal, while she played the guitar. Both the events expressed in the simple past tense, occurring at the same time period in past. This is not the intended meaning. Correct usage will be of the past perfect tense.

C) by killing coyotes, wolves would reverse the mesopredator overpopulation that had occurred when wolves had been
 This choice has both "would" and "had been" but it has an error in "had occurred", it distorts the timeline

D) wolves, by killing coyotes, will reverse the mesopredator overpopulation that had occurred when wolves were
 This reverses the timeline. As per this choice. Timeline is Overpopulation occured -> wolves eliminated. This is not the correct timeline.

E) wolves would, by killing coyotes, reverse the mesopredator overpopulation that occurred when wolves had been
  This answer choice presents the correct timeline by using the correct sequencing of events by using correct verb-tenses. Wolves would (by killing coyotes) reverse X that occurred when wolves had been eliminated a century ago. This precisely presents the sequence. Hence, the correct choice.

kantapong · Answer

This question is about verb tense:
A. will - occurring - were (eliminated: 50 years ago, cannot use will)
B. would - occurred - were (eliminated: 100 years earlier)
C. would - had occurred - had been (two latter events do not occur at the same time)
D. will - had occurred - were (eliminated: 50 years ago, cannot use will)
E. would - occurred - had been (correct answer)

Timeline: wolves eliminated from region -> mesopredator overpopulation -> wolves reverse

agarwal1993 · Answer

IMO B is the correct answer. Took me 2:20 minutes to decide between B and E. A very good question to brush up verb tense concepts.

Fifty years ago, ecologists studying wolf recolonization down from Canada into Washington State hypothesized that by killing coyotes, wolves will reverse the mesopredator overpopulation occurring when wolves were eliminated from this region nearly a century earlier.

Let's cut the fluff first, we get- by killing coyotes, wolves will reverse the mesopredator overpopulation occurring when wolves were eliminated from this region nearly a century earlier.

Meaning-
1- Wolves might reverse m overpopulation. How? by killing coyotes.
2- m overpop occured when- wolves were eliminated nearly 100 years back. (very important to understand this bit)

The glaring error in the original choice is the use of 'will' (future tense, also used when we definitely know that the action will occur in the future without fail). Ecologists have hypothesised. Therefore, even they can not be sure that the action they are suggesting will happen definitely . Therefore, we must use 'would' instead of 'will'. 'Would' suggests that there is a probability (not 100%) that the action will occur.

Reject A, D.

B- No errors. Let's get back to this answer choice later.
C- "by killing coyotes, wolves would reverse the mesopredator overpopulation that had occurred when wolves had been"
E- "wolves would, by killing coyotes, reverse the mesopredator overpopulation that occurred when wolves had been"

When we see two actions that happened in the past, we get excited to use past perfect tense. And, in the excitement, we forget that there are two conditions that one must always keep in mind when using the perfect tense-
1- The two actions must not be independent of each other.
2- The use of past perfect is not 'compulsory' when some words or a phrase already provides the time context in the sentence. (for example, "nearly a century earlier" in the above sentence.)
Refer this- https://gmatclub.com/blog/2016/05/past- ... orrection/
A must read article.

That being said, let's see the errors in C, E.
C- 'that had occurred'- this phrase suggests that the action of occurring happened before some other past action not independent of occuring. There is no such past action in the sentence. 'hypothesised' is an independent action, and has no link with 'had occurred'. Additionally, use of past perfect continuous 'had been eliminated' is incorrect. Use of continuous tense means that the action of elimination is still happening. But this does not make sense, and is not the intended meaning. Choice E is incorrect for the same error.

That leaves us with B.

TarunKumar1234 · Answer

Fifty years ago, ecologists studying wolf recolonization down from Canada into Washington State hypothesized that by killing coyotes, wolves will reverse the mesopredator overpopulation occurring when wolves were eliminated from this region nearly a century earlier.

Timeline of events as per the stimulus. Wolves eliminated -> Mesopredator overpopulation occurs -> Ecologists (50 years back) hypothesise -> wolves will kill the coyotes and reverse the phenomenon

By creating a timeline of events in your head, it helps in determining the correct tense usage. So, let's see which answer choices use the best tenses and convey the intended meaning.

A) by killing coyotes, wolves will reverse the mesopredator overpopulation occurring when wolves were
Ecologists hypothesised (past tense), correct tense to be used while expressing future from past- "would" not will

B) by killing coyotes, wolves would reverse the mesopredator overpopulation that occurred when wolves were
This answer choice is close by not perfect. By using simple past tense "when wolves were" it doesn't convey the correct timeline. It makes it seem that the coyote's overpopulation and the elimination of wolves were two simultaneous events. Eg: He cooked the meal, while she played the guitar. Both the events expressed in the simple past tense, occurring at the same time period in past. This is not the intended meaning. Correct usage will be of the past perfect tense.

C) by killing coyotes, wolves would reverse the mesopredator overpopulation that had occurred when wolves had been
This choice has both "would" and "had been" but it has an error in "had occurred", it distorts the timeline

D) wolves, by killing coyotes, will reverse the mesopredator overpopulation that had occurred when wolves were
This reverses the timeline. As per this choice. Timeline is Overpopulation occured -> wolves eliminated. This is not the correct timeline.

E) wolves would, by killing coyotes, reverse the mesopredator overpopulation that occurred when wolves had been
This answer choice presents the correct timeline by using the correct sequencing of events by using correct verb-tenses. Wolves would (by killing coyotes) reverse X that occurred when wolves had been eliminated a century ago. This precisely presents the sequence. Hence, the correct choice.

dinubisht003 · Answer

C is the correct answer as there are two activities happened in past in which the wolf elimination occurred earlier than overpopulation of coyotes

Posted from my mobile device

piyushluniya · Answer

Hi, In this sentence the timeline is clearly specified i.e the action of "hypothesized" happened 50 years earlier and the other 2 actions i.e "occurred & eliminated" took place a century earlier, so the use of past perfect tense is optional. So both B and C looks good to me. Can anyone please explain ?

Shaajiib · Answer

I think it supposed to be optio B. Can anyone explain me what is the problem with B?

Posted from my mobile device

zanto · Answer

I would like help understanding why C is correct? I chose E. I was thrown off by "by killing coyotes"

Ratisbon1993 · Answer

I picked C.

Here is my elimination method using splits of (1) will vs. would and (2) simple past tense vs. past perfect

A) by killing coyotes, wolves will reverse the mesopredator overpopulation occurring when wolves were  future stated from point of the past should be expressed as a hypothetical as we're not sure it'll actually happen if we make a prediction from the past - it also says "hypothesized" so "would" is the right verb here

B) by killing coyotes, wolves would reverse the mesopredator overpopulation that occurred when wolves were   there are two time points at play: (1) the time 50 years ago when ecologists hypothesized and in the question stem this is expressed as the past tense (2) the time when mesopredator population occurred because of the number of wolves going down which happened 100 years ago ("century") - In this sentence the elimination amd overpopulation happened at a time point earlier than scientists hypothesized so both "occur" and "is" should take the past perfect to denote this difference in timeline --> had occurred and had been

C) by killing coyotes, wolves would reverse the mesopredator overpopulation that had occurred when wolves had been  right answer

D) wolves, by killing coyotes, will reverse the mesopredator overpopulation that had occurred when wolves were  "would" should be used instead of "will"

E) wolves would, by killing coyotes, reverse the mesopredator overpopulation that occurred when wolves had been occurred is not in the past perfect as it should be to denote that it happened earlier than the scientists hypothesizing

generis · Answer

The official explanation is  here .

Fifty years ago ecologists studying wolf recolonization down from

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GMAT Sentence Correction (SC - EA only) Questions

Fifty years ago ecologists studying wolf recolonization down from

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