Recently physicians have determined that stomach ulcers

Question

Recently physicians have determined that stomach ulcers are not caused by stress, alcohol, or rich foods, but a bacterium that dwells in the mucous lining of the stomach.

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

The sentence talks about something physicians have determined recently. They have determined that stomach ulcers are

  1. not caused by stress, alcohol, or rich foods
  2. but a bacterium that dwells in the mucous lining of the stomach.

The sentence has a list of two elements joined through an idiom ‘not…but’. These two elements need to be parallel. However, we can see that ‘caused by stress…” and “a bacterium” are not parallel. Therefore, the original sentence has a parallelism error.

Option Analysis

(A) Incorrect. For the error described above.

(B) Incorrect. “caused by stress” and “are by a bacterium” are not parallel. The first one is a verb-ed modifier; the second is a verb.

(C) Correct. “by stress…” and “by a bacterium…” are parallel. Both are prepositional phrases playing the same role in the sentence.

(D) Incorrect. “by stress” and “a bacterium” are not parallel. The first is a prepositional phrase; the second is a noun.

(E) Incorrect. “by stress” and “are by a bacterium” are not parallel. The first is a prepositional phrase; the second one starts with a verb.

About Chiranjeev Singh

An Alumnus of IIM Ahmedabad and with a score 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 +91 9971 0010 67 or CJ@GMATwithCJ.com. He conducts online sessions for students across the world.

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