请教大全766

766.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
(E) in higher concentrations when asleep than when awake

答案：D

为什么E不对啊？请指教，谢谢。