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In laboratory rats

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by GMATsid2016 » Tue Nov 15, 2016 9:26 am
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


OAC

Please explain each options.
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by ceilidh.erickson » Tue Nov 15, 2016 3:45 pm
This question is testing PARALLELISM.

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
The conjunction "BUT" signals that we need parallelism: ______ but not _______.
The parallel construction would be "... that promotes... but does not interfere..." The word "interfering" is not parallel; it's a present participle, while "promotes" is a tensed verb.

(B) a substance that promotes blood clotting, but not seriously interfering
Same issue as in A. The distinction between "which is a substance..." and "a substance..." is meaningless.

(C) a substance that promotes blood clotting, but does not seriously interfere
Correct! "promotes" and "does not interfere" are parallel, and there are no other errors.

(D) which is a substance to promote blood clotting, but does not seriously interfere
"... to promote... but does not interfere..." is not a parallel construction. We can't have one infinitive and one tensed verb in a parallel list.

(E) which is a substance that promotes blood clotting, but not a serious interference
"that promotes... but not a[n] interference...." is not a parallel construction. We can't have one verb and one action noun in a parallel list.

The answer is C.
Ceilidh Erickson
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by ceilidh.erickson » Tue Nov 15, 2016 3:59 pm
For more on parallelism, see:
https://www.beatthegmat.com/how-to-id-pa ... tml#547586
https://www.beatthegmat.com/birds-fallin ... tml#554788
https://www.beatthegmat.com/good-questio ... tml#699680
https://www.beatthegmat.com/q17-og13-res ... tml#558413
https://www.beatthegmat.com/ron-s-favori ... tml#572845
https://www.beatthegmat.com/comparison-q ... tml#782937
https://www.beatthegmat.com/new-york-cit ... tml#715501
Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education
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by GMATsid2016 » Wed Nov 16, 2016 8:25 am
ceilidh.erickson wrote:This question is testing PARALLELISM.

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
The conjunction "BUT" signals that we need parallelism: ______ but not _______.
The parallel construction would be "... that promotes... but does not interfere..." The word "interfering" is not parallel; it's a present participle, while "promotes" is a tensed verb.

(B) a substance that promotes blood clotting, but not seriously interfering
Same issue as in A. The distinction between "which is a substance..." and "a substance..." is meaningless.

(C) a substance that promotes blood clotting, but does not seriously interfere
Correct! "promotes" and "does not interfere" are parallel, and there are no other errors.

(D) which is a substance to promote blood clotting, but does not seriously interfere
"... to promote... but does not interfere..." is not a parallel construction. We can't have one infinitive and one tensed verb in a parallel list.

(E) which is a substance that promotes blood clotting, but not a serious interference
"that promotes... but not a[n] interference...." is not a parallel construction. We can't have one verb and one action noun in a parallel list.

The answer is C.
Hello Ceilidh ,

Thanks for your reply.

Can you please also advise that the usage of WHICH is correct?


Thanks,

Sid
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by ceilidh.erickson » Wed Nov 16, 2016 12:56 pm
Either usage would be correct:
...thromboxane, which is a substance that promotes...
...thromboxane, a substance that promotes...

The first would be a modifying dependent clause, the second is a modifying appositive (noun). Both are perfectly grammatically correct. When that's the case, the right answer will almost always be the more concise one - in this case, the appositive.

However, the GMAT will not make you choose between two grammatically correct options based on concision alone.
Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education
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