NASA’s methodical approach to the exploration of Mars has not yet answ

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Here is a detailed explanation to this question-
Meaning is crucial to solving this problem:
Understanding the intended meaning is key to solving this question; the intended meaning of the crucial part of this sentence is that NASA’s methodical approach to the exploration of Mars has not yet answered whether fossil traces left by biological lifeforms on Mars still exist in some moist recesses of the cold and arid planet.

Concepts tested here: Meaning + Verb Forms + Pronouns + Idioms + Awkwardness/Redundancy

• Actions that concluded in the past are conveyed through the simple past tense.
• “if” is used to refer to phrases that lead to a “then” clause, and “whether" is used for showing alternatives; "whether" generally wins over "if" on GMAT.

A:
1/ This answer choice alters the meaning of the sentence through the phrase "can still exist"; the use of "can" incorrectly implies that NASA’s methodical approach to the exploration of Mars has not yet answered whether it is possible for fossil traces left by biological lifeforms on Mars to still exist in some moist recesses of the cold and arid planet; the intended meaning is that NASA’s methodical approach to the exploration of Mars has not yet answered whether fossil traces left by biological lifeforms on Mars practically still exist in some moist recesses of the cold and arid planet.
2/ Option A incorrectly uses the present participle ("verb+ing") phrase "having left" to refer to an action that concluded in the past; remember, actions that concluded in the past are conveyed through the simple past tense.

B:
1/ This answer choice alters the meaning of the sentence through the phrase "whether...can those traces"; the construction of this phrase leads to an incoherent meaning; the intended meaning is that NASA’s methodical approach to the exploration of Mars has not yet answered whether fossil traces left by biological lifeforms on Mars still exist in some moist recesses of the cold and arid planet.
2/ Option B uses the needlessly wordy phrase "if it is presumed that", leading to awkwardness and redundancy.

C: Correct.
1/ This answer choice uses the phrase "whether...those traces still exist", conveying the intended meaning - that NASA’s methodical approach to the exploration of Mars has not yet answered whether fossil traces left by biological lifeforms on Mars practically still exist in some moist recesses of the cold and arid planet.
2/ Option C correctly uses the simple past tense verb "left" to refer to an action that concluded in the past.
3/ Option C correctly uses "whether" to show alternatives.
4/ Option C avoids the pronoun ambiguity seen in Options D and E, as it uses no pronouns.
5/ Option C is free of any awkwardness or redundancy.

D:
1/ This answer choice alters the meaning of the sentence through the phrase "can still exist"; the use of "can" incorrectly implies that NASA’s methodical approach to the exploration of Mars has not yet answered whether it is possible for fossil traces left by biological lifeforms on Mars to still exist in some moist recesses of the cold and arid planet; the intended meaning is that NASA’s methodical approach to the exploration of Mars has not yet answered whether fossil traces left by biological lifeforms on Mars practically still exist in some moist recesses of the cold and arid planet.
2/ Option D incorrectly uses "if" to show alternatives; remember, “if” is used to refer to phrases that lead to a “then” clause, and “whether" is used for showing alternatives; "whether" generally wins over "if" on GMAT.
3/ Option D suffers from pronoun ambiguity, as it is unclear whether "they" refers to "biological life forms" or "fossil traces".
4/ Option D uses the needlessly wordy phrase "did leave", leading to awkwardness and redundancy.

E:
1/ This answer choice incorrectly uses "if" to show alternatives; remember, “if” is used to refer to phrases that lead to a “then” clause, and “whether" is used for showing alternatives; "whether" generally wins over "if" on GMAT.
2/ Option E suffers from pronoun ambiguity, as it is unclear whether "they" refers to "biological life forms" or "fossil traces".
3/ Option E uses the needlessly wordy phrase "to have left", 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 (~2 minutes):



To understand the concept of "If" versus "Whether" on GMAT, you may want to watch the following video (~1 minute):



All the best!
Experts' Global Team