Sentence Correction

In large doses, analgesics that work in the brain as antagonists to certain chemicals have caused psychological disturbances in patients, which may limit their potential to relieve severe pain.
(A) which may limit their potential to relieve
(B) which may limit their potential for relieving
(C) which may limit such analgesics’ potential to relieve
(D) an effect that may limit their potential to relieve
(E) an effect that may limit the potential of such analgesics for relieving


E is right answer..how?

In large doses, analgesics that work in the brain as antagonists to certain chemicals have caused psychological disturbances in patients, which may limit their potential to relieve severe pain.

(A) which may limit their potential to relieve - What is "their" analgesics or patients? ambiguous
(B) which may limit their potential for relieving- Same as above
(C) which may limit such analgesics’ potential to relieve- Which is it used for non-essential elements, in this case the effect of the analgesics is essential
(D) an effect that may limit their potential to relieve - problem with their again
(E) an effect that may limit the potential of such analgesics for relieving- YES

Adding to isis's comments, this is a commonly tested element on the GMAT.

Whenever "which" is used to refer to the entire clause preceeding it
or an action described in the clause preceeding it, it is almost always
incorrect.

If one were to apply the 2/3 principle here, one can eliminate A, B and C
based on the usage of "which" and then narrow down on just D and E.
D clearly has an incorrect pronoun (their) usage.

thank u so much

I'll go with E