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Here is a detailed explanation to this question-
pmal04 wrote:
Source : GMATPrep Default Exam Pack
The first detailed study of magpie attacks in Australia indicates that by the time they had reached adulthood, 98 percent of men and 75 percent of women born in the country have been attacked by the birds.
(A) by the time they had reached adulthood, 98 percent of men and 75 percent of women born in the country have been attacked by the birds
(B) by the time they reach adulthood, 98 percent of men and 75 percent of women, who were born in the country, had been attacked by the birds
(C) by the time they reached adulthood, 98 percent of men and 75 percent of women born in the country had been attacked by the birds
(D) 98 percent of men and 75 percent of women that were born in the country were attacked by the birds by the time they reach adulthood
(E) 98 percent of men and 75 percent of women who were born in the country, by the time they reached adulthood had been attacked by the birds
Concepts tested here: Tenses + Pronouns + Awkwardness/Redundancy• 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 with the action that took place most recently.
• The simple past tense is used to refer to actions that concluded in the past.
• 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.
• 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.
• "that" cannot be used to refer to a human being.
A: This answer choice incorrectly uses the past perfect tense verb "had reached" to refer to the later of two actions that concluded in the past - the men and women born in Australia being attacked by magpies and the men and women reaching adulthood; remember, 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 with the action that took place most recently. Further, Option A incorrectly uses the present perfect tense verb "have been attacked" to refer to the earlier of two actions that concluded in the past - the men and women born in Australia being attacked by magpies and the men and women reaching adulthood; remember, 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 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.
B: This answer choice incorrectly uses the simple present tense verb "reach" to refer to the later of two actions that concluded in the past - the men and women born in Australia being attacked by magpies and the men and women reaching adulthood; remember, 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 with the action that took place most recently; 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. Further, Option B uses the needlessly wordy phrase "who were born in the country", leading to awkwardness and redundancy.
C: Correct. This answer choice correctly uses the simple past tense verb "reached" and the past perfect tense verb "had been attacked" to refer to the later and earlier of two actions that concluded in the past - the men and women born in Australia being attacked by magpies and the men and women reaching adulthood - respectively. Further, Option C avoids the pronoun error seen in Option D, as it does not use the pronoun "that". Additionally, Option C is free of any awkwardness or redundancy.
D: This answer choice incorrectly uses "that" to refer to "98 percent of men and 75 percent of women"; please remember, "that" cannot be used to refer to a human being. Further, Option D incorrectly uses the simple past tense verb "were attacked" to refer to the earlier of two actions that concluded in the past - the men and women born in Australia being attacked by magpies and the men and women reaching adulthood; remember, 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 with the action that took place most recently. Additionally, Option D incorrectly uses the simple present tense verb "reach" to refer to the later of two actions that concluded in the past - the men and women born in Australia being attacked by magpies and the men and women reaching adulthood; remember, 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 with the action that took place most recently; 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.
E: This answer choice uses the needlessly wordy phrase "who were born in the country", leading to awkwardness and redundancy.
Hence, C 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
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