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In preparation for the Sentence Correction portion of the GMAT, let’s go over a great question asked by one our students, Mike, about an especially deceptive GMATPrep® SC problem. Mike’s question is about the proper use of the past perfect tense, which you’ll recall is used to indicate that one past event occurred before another past event. Try the problem, then read on to see where Mike got tripped up:

His studies of ice-polished rocks in his Alpine homeland, 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 what are now temperate areas.

(A) in which great ice sheets had existed in now currently temperate areas
(B) in which great ice sheets existed in what are now temperate areas
(C) when great ice sheets existed where there were areas now temperate
(D) when great ice sheets had existed in current temperate areas
(E) when great ice sheets existed in areas now that are temperate

Do you have your answer? Then read on!

The problem with the original sentence is a matter of verb tense. Mike’s question: Why is “had existed” incorrect? The ice sheets existed in a time prior to the time when “his studies led Louis Agassiz in 1837 to propose…,” so shouldn’t the past perfect tense be used here?

Answer: This is a tricky tense issue and is a great example of how context determines verb tense. It is true that the ice sheets existed in a time prior to when “his studies led Louis Agassiz in 1837 to propose,” but that event does not factor into the tense relationship.

Agassiz proposed a theory that ice sheets used to exist in areas where they no longer do. The time relationship presented by the theory is between the present (“now”) and the past (“existed”). Since Agassiz compares the present to the past, the tense relationship should be the present tense and the simple past.

Yes, Agassiz proposed this theory in the past, but the time relationship within the theory’s claim is unchanged by when it was proposed. The past perfect is used when two past tense events are described and one must be distinguished from the other as having occurred first. This is not the case here.

To help clarify this concept, check out this example:

Yesterday, my friend told me that dinosaurs roamed the earth.

The dinosaurs’ roaming the earth occurred before my friend’s telling me, but we should not use the past perfect “had roamed” here because we are not distinguishing one as occurring first. My friend told me something that happened in the past, regardless of when he told me, so we use the simple past to describe this information.

Apart from the verb tense error, choice A is incorrect because “now currently” is redundant. In choice C, “where there were areas now temperate” is wordy and confusing. Choice D contains the adjective  ”current,” which should be the adverb “currently” since it’s modifying the adjective “temperate,” not the noun “areas.” In choice E, since “now” is an adverb, it should be placed immediately before or after “are,” the verb it modifies.

That just leaves choice B, the correct answer to this question.

So to Mike and his fellow studiers, remember that the past perfect is used to indicate deliberately that one event occurred before another event in the past.