Some patients who do not respond to therapies

[BTGmoderatorDC]

Some patients who do not respond to therapies for depression may simply have received inadequate treatment, having, for example, been prescribed a drug at a dosage too low to be effective or having been taken off a drug too soon.

A. having, for example, been prescribed a drug at a dosage too low to be effective or having been
B. having, for example, a drug prescription that was ineffective because the dosage was too low, or being
C. as, for example, having too low of a dosage of a prescribed drug for it to be effective, or being
D. when they have, for example, been prescribed too low a drug dosage to be effective, or were
E. for example, when they have a drug prescription with a dosage too low to be effective, or been

I'm having a hard time figuring what is wrong with Option C? Can some experts explain?

OA A

[EconomistGMATTutor]

Hello!

The problem with answer C is that changing the word "having" to "as" requires the writer to change the verb tense in the rest of the sentence. By doing this, the sentence now has inconsistent verb tenses throughout the sentence. Here is a breakdown of just the verbs in each answer:

Answer A (Correct): have received / having been prescribed / having been taken off
Answer C (Incorrect): have received / having / being

As you can see, in answer A, all of the verbs are present perfect tense. However, in answer C, the last two verbs are not in present perfect tense. To help make sure the answer uses consistent verbs, I also suggest reading them without the interrupting phrase "for example," which is there to confuse test takers.

I'm available if you'd like any follow up.