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BillyZ
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GMAT 1: 750 Q51 V40 (Online)
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B
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
85%
(hard)
Question Stats:
47% (02:11) correct
53%
(02:12)
wrong
based on 1905
sessions
History
Date
Time
Result
Not Attempted Yet
Genetic research suggests that after cheetah ancestors had migrated from North America to Asia more than 100,000 years ago, when sea levels were thought to have been much lower, they quickly spread to Africa, where the species is safe from the ice ages that have wiped out its populations on other continents.
A. had migrated from North America to Asia more than 100,000 years ago, when sea levels were thought to have been much lower, they quickly spread to Africa, where the species is safe from the ice ages that have wiped out its
B. migrated from North America to Asia more than 100,000 years ago, when sea levels are thought to have been much lower, they quickly spread to Africa, where the species was safe from the ice ages that wiped out its
C. had migrated from North America to Asia more than 100,000 years ago, when sea levels are thought to have been much lower, they quickly spread to Africa, where the species was safe from the ice ages that wiped out their
D. migrated from North America to Asia more than 100,000 years ago, when sea levels are thought to be much lower, they quickly spread to Africa, where the species has been safe from the ice ages that wiped out its
E. migrated from North America to Asia more than 100,000 years ago, when sea levels were thought to have been much lower, they quickly spread to Africa, where the species is safe from the ice ages that wiped out their
This problem offers a variety of decision points related to verb tenses and pronouns, and the key to solving it correctly lies in determining which decisions are fatally flawed - they provide an illogical, incorrect meaning - and which are more a matter of preference.
For example, the first major difference - "had migrated" vs. "migrated" - is really just a matter of preference. The past-perfect "had migrated" puts extra emphasis on the sequence of events, but the simple past "migrated" works just as well (think about it - saying "after I finished at the gym, I took a shower" works just as well as "after I had finished at the gym, I took a shower").
One completely illogical verb choice in this problem, however, is the "were thought to be" (or "were thought to have been") in choices A and E. The time period in question is more than 100,000 years ago, so "were" puts that "thought to be" in that timeframe. And clearly no one was thinking about sea level comparisons back then - that's current scientific analysis, so you must have "when sea levels are thought" with the "are" putting the thinking in the present.
Choice D commits a similar error: while the thinking "are thought to be" is in the proper, current tense, the verb "to be" there is incorrect. While the thinking is in the present tense, the lower water levels themselves were in the past, so a past-tense verb such as "are thought to have been" is required.
From there you might consider the pronoun decision between "its" and "their." The antecedent is "the species," requiring the singular "its" and helping you eliminate choice C.
Choice B uses logical verb tense and accurate pronouns throughout, and is therefore correct.
A. had migrated from North America to Asia more than 100,000 years ago, when sea levels were thought to have been much lower, they quickly spread to Africa, where the species is safe from the ice ages that have wiped out its
B. migrated from North America to Asia more than 100,000 years ago, when sea levels are thought to have been much lower, they quickly spread to Africa, where the species was safe from the ice ages that wiped out its
C. had migrated from North America to Asia more than 100,000 years ago, when sea levels are thought to have been much lower, they quickly spread to Africa, where the species was safe from the ice ages that wiped out their
D. migrated from North America to Asia more than 100,000 years ago, when sea levels are thought to be much lower, they quickly spread to Africa, where the species has been safe from the ice ages that wiped out its
E. migrated from North America to Asia more than 100,000 years ago, when sea levels were thought to have been much lower, they quickly spread to Africa, where the species is safe from the ice ages that wiped out their
OFFICIAL SOLUTION
This problem offers a variety of decision points related to verb tenses and pronouns, and the key to solving it correctly lies in determining which decisions are fatally flawed - they provide an illogical, incorrect meaning - and which are more a matter of preference.
For example, the first major difference - "had migrated" vs. "migrated" - is really just a matter of preference. The past-perfect "had migrated" puts extra emphasis on the sequence of events, but the simple past "migrated" works just as well (think about it - saying "after I finished at the gym, I took a shower" works just as well as "after I had finished at the gym, I took a shower").
One completely illogical verb choice in this problem, however, is the "were thought to be" (or "were thought to have been") in choices A and E. The time period in question is more than 100,000 years ago, so "were" puts that "thought to be" in that timeframe. And clearly no one was thinking about sea level comparisons back then - that's current scientific analysis, so you must have "when sea levels are thought" with the "are" putting the thinking in the present.
Choice D commits a similar error: while the thinking "are thought to be" is in the proper, current tense, the verb "to be" there is incorrect. While the thinking is in the present tense, the lower water levels themselves were in the past, so a past-tense verb such as "are thought to have been" is required.
From there you might consider the pronoun decision between "its" and "their." The antecedent is "the species," requiring the singular "its" and helping you eliminate choice C.
Choice B uses logical verb tense and accurate pronouns throughout, and is therefore correct.
16 Nov 2017, 13:50
Kudos
Bookmarks
csaluja
Three thoughts on this:
- 1. Like all non-official questions, this one should be taken with a grain of salt. Your questions are totally legit, but.... well, when in doubt, don't lose too much sleep over this one.
2. You could argue that "are thought to have been" is OK here, since the act of thinking is occurring now -- not 100,000 years ago. That's clearly what the question-writers were thinking, but it seems like we would typically use the past tense in this case, since the grammatical subject is technically the "sea levels" from 100,000 years ago. At the very least, I can't think of any actual GMAT questions that make you choose in circumstances like these. In other words: you have a point, and don't worry about it too much.
3. The question has it right on the "species" issue, though! There are plenty of weird nouns in English that can be either singular or plural (media or data or deer or diabetes or starfish), but the GMAT will always give you a hint about whether the word is used as a singular or plural in that specific case. And in this question, "species" is clearly singular, since all five answer choices use a singular verb ("is" or "was") with "species." So the singular pronoun "its" is appropriate later in the sentence.
I hope this helps!
27 Oct 2021, 01:16
Kudos
Bookmarks
Dear Friends,
Here is a detailed explanation to this question-
Concepts tested here: Tenses + Pronouns + Awkwardness/Redundancy
• Collective nouns (such as “species” in this sentence) are always singular.
• The simple past tense is used to refer to events that concluded in the past.
• The simple present tense is used to indicate actions taking place in the current time frame, indicate habitual actions, state universal truths, and convey information that is permanent in nature.
• The present perfect tense (marked by the use of the helping verb “has/have”) is only used to describe events that concluded in the past but continue to affect the present.
• The past perfect tense (marked by the use of the 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".
• When the chronology is clear because of terms such as "before/after/when/earlier/later"…or because of clear mention of dates, use past perfect tense is not required, though not incorrect either.
• The perfect infinitive verb form (“to + have + past participle” – “to have been” in this sentence) is used to refer to the earlier of two actions in the past, refer to hypothetical actions, and actions that will be completed in the future.
A: This answer choice incorrectly uses the simple past tense verb "were thought" to refer to an action that takes place in the current time frame; please remember, the simple present tense is used to refer to actions that take place in the current time frame, and the simple past tense is only used to refer to events that concluded in the past. Further, Option A incorrectly use the present perfect tense verb "have wiped out" 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 only used to describe events that concluded in the past but continue to affect the present. Additionally, Option A incorrectly uses the simple present tense verb "is" to refer to an action that concluded in the past; please remember, the simple past tense is used to refer to actions that concluded in the past, and the simple present tense is used to indicate actions taking place in the current time frame, indicate habitual actions, state universal truths, and convey information that is permanent in nature. Besides, Option A redundantly uses the past perfect tense verb "had migrated" alongside the word "after"; 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"; however, when the chronology is clear because of terms such as "before/after/when/earlier/later"…or because of clear mention of dates, use past perfect tense is not required, though not incorrect either.
B: Correct. This answer choice correctly refers to the singular noun "species" with the singular pronoun "its". Further, Option B correctly uses the simple present tense verb "are thought" to refer to an action taking place in the current time frame. Additionally, Option B correctly uses the perfect infinitive verb form (“to + have + past participle” – “to have been” in this sentence) to refer to the earlier of two actions that took place in the past -- sea levels being much lower 100,000 years ago and sea levels being thought to have been much lower 100,000 years ago. Additionally, Option B correctly uses the simple past tense verbs "was" and "wiped out" to refer to events that concluded in the past. Besides, Option B is free of any awkwardness or redundancy.
C: This answer choice incorrectly refers to the singular noun "species" with the plural pronoun "their"; please remember, collective nouns (such as “species” in this sentence) are always singular. Further, Option C redundantly uses the past perfect tense verb "had migrated" alongside the word "after"; 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"; however when the chronology is clear because of terms such as "before/after/when/earlier/later"…or because of clear mention of dates, use past perfect tense is not required, though not incorrect either.
D: This answer choice incorrectly uses the infinitive verb form ("to + base form of verb" - "to + be" in this sentence) construction "thought to be" to refer to the earlier of two actions that took place in the past -- sea levels being much lower 100,000 years ago and sea levels being thought to have been much lower 100,000 years ago; please remember, perfect infinitive verb form (“to + have + past participle”), rather than the infinitive verb form ("to + base form of verb"), is used to refer to the earlier of two actions in the past. Further, Option D incorrectly uses the present perfect tense verb "has been" to refer to an event 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 only used to describe events that concluded in the past but continue to affect the present.
E: This answer choice incorrectly refers to the singular noun "species" with the plural pronoun "their"; please remember, collective nouns (such as “species” in this sentence) are always singular. Further, Option E incorrectly uses the simple past tense verb 'were thought" to refer to an action that takes place in the current time frame; please remember, the simple present tense is used to refer to actions that take place in the current time frame, and the simple past tense is only used to refer to events that concluded in the past. Additionally, Option E incorrectly uses the simple present tense verb "is" to refer to an action that concluded in the past; please remember, the simple past tense is used to refer to actions that concluded in the past, and the simple present tense is used to indicate actions taking place in the current time frame, indicate habitual actions, state universal truths, and convey information that is permanent in nature.
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 (~2 minutes):
All the best!
Experts' Global Team
All the best!
Experts' Global Team
Here is a detailed explanation to this question-
BillyZ
Concepts tested here: Tenses + Pronouns + Awkwardness/Redundancy
• Collective nouns (such as “species” in this sentence) are always singular.
• The simple past tense is used to refer to events that concluded in the past.
• The simple present tense is used to indicate actions taking place in the current time frame, indicate habitual actions, state universal truths, and convey information that is permanent in nature.
• The present perfect tense (marked by the use of the helping verb “has/have”) is only used to describe events that concluded in the past but continue to affect the present.
• The past perfect tense (marked by the use of the 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".
• When the chronology is clear because of terms such as "before/after/when/earlier/later"…or because of clear mention of dates, use past perfect tense is not required, though not incorrect either.
• The perfect infinitive verb form (“to + have + past participle” – “to have been” in this sentence) is used to refer to the earlier of two actions in the past, refer to hypothetical actions, and actions that will be completed in the future.
A: This answer choice incorrectly uses the simple past tense verb "were thought" to refer to an action that takes place in the current time frame; please remember, the simple present tense is used to refer to actions that take place in the current time frame, and the simple past tense is only used to refer to events that concluded in the past. Further, Option A incorrectly use the present perfect tense verb "have wiped out" 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 only used to describe events that concluded in the past but continue to affect the present. Additionally, Option A incorrectly uses the simple present tense verb "is" to refer to an action that concluded in the past; please remember, the simple past tense is used to refer to actions that concluded in the past, and the simple present tense is used to indicate actions taking place in the current time frame, indicate habitual actions, state universal truths, and convey information that is permanent in nature. Besides, Option A redundantly uses the past perfect tense verb "had migrated" alongside the word "after"; 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"; however, when the chronology is clear because of terms such as "before/after/when/earlier/later"…or because of clear mention of dates, use past perfect tense is not required, though not incorrect either.
B: Correct. This answer choice correctly refers to the singular noun "species" with the singular pronoun "its". Further, Option B correctly uses the simple present tense verb "are thought" to refer to an action taking place in the current time frame. Additionally, Option B correctly uses the perfect infinitive verb form (“to + have + past participle” – “to have been” in this sentence) to refer to the earlier of two actions that took place in the past -- sea levels being much lower 100,000 years ago and sea levels being thought to have been much lower 100,000 years ago. Additionally, Option B correctly uses the simple past tense verbs "was" and "wiped out" to refer to events that concluded in the past. Besides, Option B is free of any awkwardness or redundancy.
C: This answer choice incorrectly refers to the singular noun "species" with the plural pronoun "their"; please remember, collective nouns (such as “species” in this sentence) are always singular. Further, Option C redundantly uses the past perfect tense verb "had migrated" alongside the word "after"; 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"; however when the chronology is clear because of terms such as "before/after/when/earlier/later"…or because of clear mention of dates, use past perfect tense is not required, though not incorrect either.
D: This answer choice incorrectly uses the infinitive verb form ("to + base form of verb" - "to + be" in this sentence) construction "thought to be" to refer to the earlier of two actions that took place in the past -- sea levels being much lower 100,000 years ago and sea levels being thought to have been much lower 100,000 years ago; please remember, perfect infinitive verb form (“to + have + past participle”), rather than the infinitive verb form ("to + base form of verb"), is used to refer to the earlier of two actions in the past. Further, Option D incorrectly uses the present perfect tense verb "has been" to refer to an event 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 only used to describe events that concluded in the past but continue to affect the present.
E: This answer choice incorrectly refers to the singular noun "species" with the plural pronoun "their"; please remember, collective nouns (such as “species” in this sentence) are always singular. Further, Option E incorrectly uses the simple past tense verb 'were thought" to refer to an action that takes place in the current time frame; please remember, the simple present tense is used to refer to actions that take place in the current time frame, and the simple past tense is only used to refer to events that concluded in the past. Additionally, Option E incorrectly uses the simple present tense verb "is" to refer to an action that concluded in the past; please remember, the simple past tense is used to refer to actions that concluded in the past, and the simple present tense is used to indicate actions taking place in the current time frame, indicate habitual actions, state universal truths, and convey information that is permanent in nature.
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 (~2 minutes):
All the best!
Experts' Global Team
All the best!
Experts' Global Team
