Sentence Correction

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

A -- having, for example been prescribed a drug as 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 prescribed drug for it to be effective, or being
D -- when they have, for example, been prescribed too low a drug dosage for it to be effective, or were
E -- for example, when they have a drug prescription with a dosage too low to be effective, or been

is th s/c correct

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

A -- having, for example been prescribed a drug as 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 prescribed drug for it to be effective, or being
D -- when they have, for example, been prescribed too low a drug dosage for it to be effective, or were
E -- for example, when they have a drug prescription with a dosage too low to be effective, or been

Indeed a toughie because the right answer does not pop out.....In such cases POE is my preferred mode of attack

B and C - courtesy my friend "being" - out you go!!!

D - "they" is placed too far to refer to "patients", especially with the word "therapies" in between.....but i would prefer another error to comprehensively rule out this option........ and there is a "Parallelism" clue - "have been prescribed" and "were taken off" not parallel - D is out

E - seems like a pronoun error again with "they" but i want to investigate for another error....and there is a parallelism error here too "they have a drug prescription" does not work with "been taken off" - E is out too

A is the only one left....it doesn't sound great at 1st, but A is the only option that maintains llsm, with a couple of "having been"...i go for "A"

let me take this as a combination of two sentences

Some patients who do not respond to therapies of depression may simply have received inadequate treatment.

they have been prescribed a drug as a dosage too low to be effective or they have been taken off the drug too soon.

(the second sentence here is in present perfect because of the ending of the first sentence which is the part of the question and in the passive voice because the action is more important than the doer.)

Now if I combine the two things I will be left with option A.

This sentence is wrong. Even if this is from the Official Guide, I will stand by this sentence being wrong.

The OA is probably choice A, but with choice A it should be worded

having, for example, been prescribed a drug as a dosage too low to be effective or having been

You have to have the comma after "for example", otherwise it is grammatically incorrect.

Final solution at one place:

Important: The purpose of this post (and all the other posts by me) is to give a complete solution to all GMAT-Prep Verbal questions at one place. Sometimes students have to wade through dozens of posts to get to the final answer. My posts will give one complete and crisp solution required to arrive at the correct answer by eliminating the wrong ones. Some of the content in these posts may have been taken from various other sources (discussion forums).

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 for it to be effective, or were
(E) for example, when they have a drug prescription with a dosage too low to be effective, or been

The best way to attack this problem is to remove 'for example' from each of the choices.

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

A is parallel 'having been || having been' ... the connector word is 'or' ... as we are joining two similar ideas (and only two ideas), we should not use a comma. This alone is sufficient to eliminate B, C, D, and E.

In B, 'having a drug prescription (refers to patients) can't be parallel to being taken off (refers to a doctor, possibly) ... as the subjects are different, the two are not parallel.

In C, 'having too low of a dosage (refers to patients) can't be parallel to being taken off (refers to a doctor, possibly) ... as the subjects are different, the two words are not parallel.

D is not parallel ('have been' is not parallel to 'were')

E is not parallel ('have a prescription' is not parallel to 'been taken off')

Correct: A