521.When Alice caome to herself,she did not know how long she _____ there.
A.had been lying
B.has been lying
C.was lying
D.has lain
522.Tom _____ in the library every night over the lsat three months.
A.works
B.worked
C.has been working
D.had been working
521.答案是A;考查动词的时态。句意:当Alice苏醒过来时，她不知道自己在那儿躺了多久了。过去完成时表示持续到过去某时之前的动作。
522.答案是C;考查动词的时态。句意:过去3个月里，Tom每天晚上都在图书馆里学习。根据题干中over the last three months的暗示可用现在完成时或现在完成进行时。
