1000 SC- #33

[tarek99]

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,


I chose option A, however, the OA is E. I don't see how and need some input. Would you be so kind to give me an explanation? thanks!

[RonPurewal]

well, first of all you have to understand the meaning of the original, including the following 2 key points:
- the periwinkle, a flower, is what's being cultivated in china.
- the derivative substance (not the periwinkle itself) is used to treat leukemia.

once you've got that out of the way:
choice a: two problems
- remember that relative-pronoun phrases (here, relative pronoun = which) after commas are generally taken to modify the noun directly preceding the comma. so this sentence says that the periwinkle itself has been used to treat leukemia patients. oops!
- the main subject of the whole sentence is substance (the rest is descriptive phrases), so the sentence is saying that the substance is cultivated in china. (to see this, cross out everything between the commas, as well as the adjective phrase derived from the madagascar periwinkle). oops!

choice e fixes both of these problems:
- the main subject of the sentence has changed to periwinkle, which is obligatory (this is the only thing that's being cultivated in china)
- the modifier has been corrected, so that it properly refers to a derivative of the periwinkle

[Guest]

thanks i really appreciate your input. that cleared my doubts. I also have another question. sometimes i see answer choices with the word "which" without the comma before it. are such constructions always wrong? i know that "which" is generally preceeded by the comma, but are there any exceptions to this rule or is it always a must?
thanks

[RonPurewal]

thanks i really appreciate your input. that cleared my doubts. I also have another question. sometimes i see answer choices with the word "which" without the comma before it. are such constructions always wrong? i know that "which" is generally preceeded by the comma, but are there any exceptions to this rule or is it always a must?
thanks

if there's no comma (which creates an 'essential modifier', if you're into linguistic terms), then that is generally preferred. you'll find general disagreement among english-language authorities as to whether which is permissible at all in this context, but there's no doubt that that is the better choice.

n.b. i doubt that a gmat problem will be decided upon that vs. which alone.

[Guest]

take a look at this for example:

[deleted - cannot host questions from unknown sources]


If you look at the sentence that is not underlined, you will find the word "which" without the comma behind it. I honestly don't know from which source this is cause I only found it in the scoretop forum. How come there is no comma before "which" in this case?
thanks

[StaceyKoprince]

Hi, guys - sorry, we can't host questions from unknown sources due to legal copyright issues. (In particular from Scoretop - they have been sued by GMAC for hosting questions without proper citation or copyright permission.)