P181

1.        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

(B) when sleeping in higher concentrations than waking hours

(C) in higher concentrations during sleeping than waking

(D) in higher concentrations during sleep than during waking hours（D）

(E) in higher concentrations when asleep than when awake

E 不可以吗？

when是引导从句的，加名词没见过，楼主不要翻译意思要想想是否符合语法规则。

LS，asleep和awake都是形容词，不是名词。连词加形容词是状语从句的省略结构。

但是该省略结构要求逻辑主语和句子主语一致，而E中when从句的逻辑主语和句子主语不一致，所以不可。