f2001290 wrote:33.A substance derived from the Madagascar periwinkle, which has proved useful in decreasing mortality among young leukemia patients, is cultivated in China as part of a program to integrate traditional herbal medicine into a contemporary system of health care.
(A) A substance derived from the Madagascar periwinkle, which has proved useful in decreasing mortality among young leukemia patients,
(B) A derivative, which has proved useful in decreasing mortality among young leukemia patients, of the Madagascar periwinkle,
(C) A Madagascar periwinkle derivative, which has proved useful in decreasing mortality among young leukemia patients,
(D) The Madagascar periwinkle has a derivative which has proved useful in decreasing mortality among young leukemia patients, that
(E) The Madagascar periwinkle, a derivative of which has proved useful in decreasing mortality among young leukemia patients,

OA is E

Can somebody explain?

Here's my take

A - which refers to periwinkle while it should refer to the derivative

B - too many fragments, awkward construction

C - which correctly refers to derivative but the derivative is not the one
that is cultivated.

D - "that" should be used instead of which

E - correct.

Spot on - OA is E

Adding explanation to old thread:

Means: A substance X derived from Y - which is proved usedful in Z-is cultivated in China for :--- here X is used but cultivation is of Y !! The correct Ans is E!!
(A) A substance X (sub)derived from the Y(obj), which(Non restrictive sentence) has proved useful in decreasing mortality among young leukemia patients, is cultivated...... means that X is cultivated instead of Y INCORRECT!
(B) A derivative, which has proved useful in decreasing mortality among young leukemia patients, of the Y, is cultivated..... again means derivative X is cultivated + also has dangling modifier -of the Y incorrect! (C) A Y derivative X, which has proved useful in decreasing mortality among young leukemia patients, is cultivated....again means X is cultivated Incorrect!
(D) The Y (sub) has a derivative X (Obj) which has proved useful in decreasing mortality among young leukemia patients, that... many erros! not clear THAT refers to X or Y + which should have either a comma or a preposition before it
(E) The Y, a derivative X of which has proved useful in decreasing mortality among young leukemia patients, is cultivated.... very clearly shows Y is cultivated Correct

The statement explains what is cultivated is Madagascar periwinkle and not its derivative.
Hence, A can be eliminated as it implies that Madagascar periwinkle has proven to be useful.
B and C are incorrect as they suggest that the derivative is cultivated.
D can be eliminated due to incorrect usage of 'that'.
E is the best choice here. Hence (e).