问题补充:
I while reading the English textbook. Luckily, my roommate woke me up in time!
A. had fallen asleep
B. have fallen asleep
C. fell asleep
D. fall asleep
答案:
A. had fallen asleep
B. have fallen asleep
(答案→)C. fell asleep
D. fall asleep
解析:while 从句用过去进行时,主句用过去时,表示在某个动作的持续过程中,发生过某事。句意为“我在读英语课本时睡着了。幸亏我的室友及时叫醒了我”。