fozzzy wrote:
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
(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
[Reveal] Spoiler:
Can someone explain C and D
Nice question. The power split on this problem is parallelism, but I haven't seen much discussion about it because it's a bit hard to see.
You have to pay attention to the core of the sentence to find the parallelism: "A low dose of aspirin usually suffices to block production of thromboxane but not seriously interfering with the production of prostacyclin." By taking out the modifiers we can see the parallelism and more easily notice the error - "suffices 'to block' ... but not 'interfering'." We can see that we need the infinitive form of interfere (remembering that the GMAT allows us to drop the leading 'to') to be parallel. A, B, and E have incorrect forms of "interfere" and get eliminated. That leaves C and D, but D gets eliminated because it's less concise and it's unclear (D really should be written "which is a substance used to promote...").
KW