Positing an enormous volcanic explosion at the end of the Permian period

Question

Positing an enormous volcanic explosion at the end of the Permian period would explain the presence of a buried crater, account for the presence of the element iridium (originating deep within the earth), and the presence of quartz having been shattered by high-impact shock waves.

Option A
Option B
Option C
Option D
Option E

(This question is from Official Guide. Therefore, because of copyrights, the complete question cannot be copied here. The question can be accessed at GMAT Club)

Solution

Sentence Analysis

Here’s the sentence structure:

  • Positing (A gerund. Main Subject)
    • an enormous volcanic explosion (Object of ‘Positing’, answering ‘positing what?’)
    • at the end of the Permian period (Prepositional phrase modifying ‘Positing’)
  • would explain the presence of a buried crater, (Main Verb: would explain)
  • account for the presence of the element iridium (‘account’ is parallel to ‘explain’ and is thus a part of the main verb)
    • (originating deep within the earth), (Verb-ing modifiers modifying ‘iridium’)
  • and the presence of quartz (Noun ‘the presence’ violates parallelism. Something parallel to ‘explain’ and ‘account’ was needed here.)
    • having been shattered by high-impact shock waves. (Perfect participle modifying ‘quartz’)

The sentence says that proposing something (a volcanic explosion) at the end of a time (the Permian period) would explain a few things: the presence of a buried crater, the presence of the element iridium, and the presence of quartz that has been shattered by shock waves.

The sentence has the following problems:

  1. Parallelism – The sentence has a deterministic error that ‘the presence of quartz’ is not parallel to ‘explain’ and ‘account’.
  2. The use of the perfect participle ‘having been shattered’ is incorrect here (Deterministic error). We are not presenting a sequence of actions here (It doesn’t make sense to sequence the actions ‘explaining the presence of quartz’ and ‘the shattering of quartz’. These are two very unrelated events). We just need to provide additional information about quartz that it was shattered by high-impact shock waves. Therefore, we need either a verb-ed modifier ‘quartz shattered by …’ or a relative clause ‘quartz that was shattered by…’.
  3. Since ‘account for’ and ‘explain’ mean the same thing, we can skip ‘account for’ in the second element of the list. This is a quality issue. On the same lines, since all the three elements of the list are about ‘the presence of something’, we need not repeat the words ‘the presence of’ in each element of the list.

Option Analysis

(A) Incorrect. For the reasons explained above.

(B) Correct. This option corrects all the problems in the originals sentence without introducing any new problem.

(C) Incorrect. For the following reasons:

  1. Parallelism (Deterministic error): ‘the element iridium’ is not parallel to the other two elements of the list ‘explain’.
  2. Same error as the 2nd error in the original sentence.

(D) Incorrect. It has a deterministic error that ‘the presence of the element iridium’ is not parallel to the other two elements of the list ‘explain’.

(E) Incorrect. For the following reasons:

  1. Parallelism (Deterministic error): ‘the presence of quartz’ is not parallel to the other two elements of the list ‘explain’.
  2. ‘explain the element iridium’ doesn’t make sense. It should be ‘explain the presence of the element iridium’.

About Chiranjeev Singh

An Alumnus of IIM Ahmedabad and with scores of 780 (2017) and 770 (2013) on GMAT and 99.98%ile on CAT, Chiranjeev is one of the most qualified GMAT tutors in India. Chiranjeev has earlier served as Director of Curriculum at e-GMAT. Chiranjeev has been helping students ace GMAT since 2012. He follows a concept-based methodology to teaching GMAT and is very committed to student success. You may contact him for any private GMAT tutoring needs at CJ@GMATwithCJ.com. He conducts online sessions for students across the world.

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