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Here is a detailed explanation to this question-
solidcolor wrote:
In Scotland, the number of wild salmon have been reduced because of uncontrolled deep-sea and coastal netting, by pollution, and by various other threats to the fish’s habitat.
A. number of wild salmon have been reduced because of uncontrolled deep-sea and coastal netting
B. number of wild salmon is reduced because deep-sea and coastal netting is not controlled
C. numbers of wild salmon has been reduced because of uncontrolled deep-sea and coastal netting
D. wild salmon’s numbers are reduced by deep-sea and coastal netting that is not controlled
E. wild salmon’s numbers have been reduced by uncontrolled deep-sea and coastal netting
Concepts tested here: Subject-Verb Agreement + Tenses + Parallelism + Awkwardness/Redundancy• All elements in a list must be parallel.
• 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.
A: This answer choice fails to maintain parallelism among "because of uncontrolled...netting", "by pollution", and "by various other...habitat"; please remember, all elements in a list must be parallel. Further, Option A uses the needlessly wordy phrase "number of wild salmon", leading to awkwardness and redundancy.
B: This answer choice incorrectly uses the simple present tense verb "is" to refer to an action that concluded in the past but continues to affect the present; please remember, 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, and the simple present tense is only 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 fails to maintain parallelism among "because... not controlled", "by pollution", and "by various other...habitat"; please remember, all elements in a list must be parallel. Additionally, Option B uses the needlessly wordy phrase "number of wild salmon", leading to awkwardness and redundancy.
C: Correct. This answer choice incorrectly refers to the plural noun "numbers" with the singular verb "has been". Further, Option C fails to maintain parallelism among "because of uncontrolled...netting", "by pollution", and "by various other...habitat"; please remember, all elements in a list must be parallel. Additionally, Option C uses the needlessly wordy phrase "numbers of wild salmon", leading to awkwardness and redundancy.
D: This answer choice incorrectly uses the simple present tense verb "are" to refer to an action that concluded in the past but continues to affect the present; please remember, 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, and the simple present tense is only 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. Additionally, Option D uses the needlessly wordy phrase "that is not controlled", leading to awkwardness and redundancy.
E: This answer choice correctly refers to the plural noun "numbers" with the plural verb "have been". Further, Option E correctly uses the present perfect tense verb "have been" to refer to an action that concluded in the past but continues to affect the present. Additionally, Option E maintains parallelism among "by...netting", "by pollution", and "by various other...habitat". Besides, Option E is free of any awkwardness to redundancy.
Hence, E 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 "Present Perfect Tense" on GMAT, you may want to watch the following video (~2 minutes):
All the best!
Experts' Global Team