Sentence Correction

Test1-35. (26325-!-item-!-188;#058&002592)

In laboratory rats, a low dose of aspirin usually suffices to block production of thromboxane, which is a substance that promotes blood clotting, but not seriously interfering with the production of prostacyclin, which prevents clotting.
(A) which is a substance that promotes blood clotting, but not seriously interfering
(B) a substance that promotes blood clotting, but not seriously interfering
(C) a substance that promotes blood clotting, but does not seriously interfere
(D) which is a substance to promote blood clotting, but does not seriously interfere
(E) which is a substance that promotes blood clotting, but not a serious interference

Ans: [spoiler](C) [/spoiler]

Why is [spoiler](D)[/spoiler] wrong?

A substance that promotes .... but does not interfere is parallel in structure while " which is a substance to promote but does not " seems unparallel to me

In that case whats wrong with B ???

this is an example of difference between use of 'that' and 'which'

we know 'which' is a non restrictive clause (extra information clauses) and 'that' is a restrictive clause (necessary information clauses). In this sentence clear indication is provided to the substance 'aspirin' for blocking production of thromboxane.

Use of 'which is a substance' is therefore redundant and a more concise use is 'a substance'. Also notice the use of 'that'

In option B check 'block' it's not 'blocking', which would have probably gone with 'interfering'

bhumika.k.shah wrote:In that case whats wrong with B ???

Promotes and interfering are not parallel in B

o okay!
i tried to make interfering parallel with clotting...
hmmmmmm!!! wondering what i was really thinking while going for option B instead of C