问题
选择题
—Show me your permit, please.
—Oh, it's not in my pocket. It ________.
A．must have fallen out
B．might fall out
C．could fall out
D．should have fallen out
答案
答案：A
A 考察情态动词。句义：请给我看你的准入证。哦！证件不在我的口袋里，肯定掉了。Must have done表示对过去事情的肯定推测。意为：一定做了某事。故A正确。