问题补充:
Henry must have stayed up last night, he looks so tired and sleepy.
A. for
B. as
C. though
D. since
答案:
(答案→)A. for
B. as
C. though
D. since
解析:考察连词。A.因为 B.因为;随着 C. 尽管 D. 因为;既然。for表示所说的理由是一种补充说明, since和as是从属连词,说明的是已为人们所知和理由。句意:亨利昨晚肯定熬夜了。因为他看起来如此累和困乏。结合语境可知选A。