Both "asleep" and "awake" are adjectives, so they have to modify a noun and the only noun is the hormone. This means that the hormones sleep which is illogical.

On the other hand, "sleep" and "waking hours" are nouns and stand on their own. In this sentence the hormones are not doing the sleeping.

KW
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'D' is the best.

(A) during sleep in higher concentrations than when awake **incorrect usage of when. Harmones does not awake****
(B) when sleeping in higher concentrations than waking hours **same as in A***
(C) in higher concentrations during sleeping than waking ***'during sleeping is compared to 'waking'*****
(D) in higher concentrations during sleep than during waking hours ****CORRECT***
(E) in higher concentrations when asleep than when awake ****Same as in 'A'***

Hey All,

Lots of good discussion here, and I think the right answer was explained here and there in pieces. I thought I'd take a stab at putting it all together in one place.

The human growth hormone, made by the pituitary gland, is secreted during sleep in higher concentrations than when awake.

(A) during sleep in higher concentrations than when awake
PROBLEM: "When" is a relative pronoun, meaning it's a modifier, meaning it has to modify something. Relative pronouns always modify nouns, but there is no adequate noun. Who is "awake" in the phrase, "when awake" (something has to be).

(B) when sleeping in higher concentrations than waking hours
PROBLEM: Again, who's sleeping?

(C) in higher concentrations during sleeping than waking
PROBLEM: This sounds like the comparison is between time spent asleep and time spent WAKING UP. The comparison should be between being asleep and being awake.

(D) in higher concentrations during sleep than during waking hours
ANSWER: Gets rid of "When" and compares the right two things.

(E) in higher concentrations when asleep than when awake
PROBLEM: Two "Whens" = double the trouble.

Hope that helps!

-tommy

D is correct.

E may imply that the hormone itself is asleep or awake.

but why cannot D mean that it is secreted during the hormone's sleep rather than its waking hours? I mean, is there rule that explain the difference between using D and E?

Hi gmatninja,

One small query wrt Choice E: Is the Comparison right in terms of singular/plural, as SLEEP looks to be singular and WAKING HOURS is plural.

Please CLARIFY,

Regards.

Posted from my mobile device

Here's the official explanation provided by the GMAC for this question:

The sentence describes a difference between being asleep and being awake with respect to secretion of the human growth hormone which is secreted in higher concentrations during sleep. The word than is correctly used to make the comparison, except that the phrases during sleep and when awake are not parallel as required. The phrase during sleep is an adverbial modifier of the verb is secreted, but the phrase when awake is an elliptical clause; when [“person X” is] awake, where “person X” should refer to something that could be awake (we know something refers to a person because the sentence is about the human growth hormone). Therefore, the lack of reference to a person indicates that when awake is incorrect in this context.

Option A: This is incorrect for the reasons given above.

Option B: The sentence contains no reference to a person to whom the verbal adjective sleeping can appropriately apply. The adverbial phrase in higher concentrations should precede sleeping to avoid a reading that seems odd, given that sleeping does not come in varying concentrations. Also, the placement of the phrase immediately before than seems to absurdly compare concentrations with waking hours. Alternatively, but equally absurd, the sentence could be read as comparing the human growth hormone with waking hours.

Option C: There is a failure of parallelism in that during is needed in the second part of the comparison as well as in the first. Also, the noun sleep would be preferable to the verb-derived noun form sleeping following during (this consideration also makes waking, the form parallel to sleeping, less suitable).

Option D: Correct. The phrases during sleep and during waking hours are parallel as required for comparisons that use than.

Option E: Although when asleep is parallel with when awake, there is no reference to a person to whom the adjectives asleep and awake can apply. This wording absurdly seems to attribute these adjectives to the human growth hormone itself.

The correct answer is D.

Please note that I'm not the author of this explanation. I'm just posting it here since I believe it can help the community.
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