A huge flying reptile that died out with the dinosaurs some 65 million

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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 core meaning of this sentence is that the Quetzalcoatlus had a wingspan of 36 feet and is believed to have been the largest flying creature the world has ever seen.

Concepts tested here: Meaning + Modifiers + Tenses + Pronouns

• The pronoun “that” is used to refer to a variation of the subject, and the pronoun “it” is used to refer to the exact same subject.
• In a “noun + comma + phrase” construction, the phrase must correctly modify the noun; this is one of the most frequently tested concepts on GMAT sentence correction.
• "who/whose/whom/which/where", when preceded by a comma, refers to the noun just before the comma.
• 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: Trap. This answer choice incorrectly modifies "wingspan of 36 feet" with "believed to be...ever seen", illogically implying that a wingspan of 36 feet is believed to have been the largest flying creature the world has ever seen; the intended meaning is that the Quetzalcoatlus is believed to have been the largest flying creature the world has ever seen; please remember, in a “noun + comma + phrase” construction, the phrase must correctly modify the noun; this is one of the most frequently tested concepts on GMAT sentence correction. Further, Option A incorrectly uses the simple present tense verb "be" to refer to an event 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 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.

B: Trap. This answer choice incorrectly uses the simple present tense verb "be" to refer to an event 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 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 incorrectly uses "that" to refer to the exact same subject - "the Quetzalcoatlus"; please remember, the pronoun “that” is used to refer to a variation of the subject, and the pronoun “it” is used to refer to the exact same subject.

C: Correct. This answer choice uses the phrase "and it is believed", avoiding the meaning errors seen in Options A, D, and E and conveying the intended meaning - that Quetzalcoatlus is believed to have been the largest flying creature the world has ever seen. Further, Option C correctly uses the present perfect tense verb "have been" to refer to an event that concluded in the past but continues to affect the present. Additionally, Option C correctly uses the pronoun "it" to refer to the exact same subject - "the Quetzalcoatlus".

D: This answer choice incorrectly refers to "wingspan of 36 feet" with "which was, it is believed...ever seen", illogically implying that a wingspan of 36 feet is believed to have been the largest flying creature the world has ever seen; the intended meaning is that the Quetzalcoatlus is believed to have been the largest flying creature the world has ever seen; please remember, "who/whose/whom/which/where", when preceded by a comma, refer to the noun just before the comma.

E: This answer choice incorrectly refers to "wingspan of 36 feet" with "which is...ever seen", illogically implying that a wingspan of 36 feet is believed to have been the largest flying creature the world has ever seen; the intended meaning is that the Quetzalcoatlus is believed to have been the largest flying creature the world has ever seen; please remember, "who/whose/whom/which/where", when preceded by a comma, refer to the noun just before the comma. Further, Option E incorrectly uses the simple present tense verb "be" to refer to an event 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 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, C is the best answer choice.

To understand the concept of "Phrase Comma Subject" and "Subject Comma Phrase" on GMAT, you may want to watch the following video (~1minute):



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