下列表现为虚劳的特点的有（）

A.神疲乏力

B.倦怠

C.形羸面黄

D.舌嫩脉弱

E.潮热盗汗

The boy was so tired that he fell asleep _______ his mother could take off his clothes.

A．before

B．after

C．while

D．when