题目

— Show me your permit, please.     —Oh, it's not in my pocket. It_______________. A. might fall out                B. could fall out C. should have fallen out        D. must have fallen out 答案：D 解析: 本题答句中fall out的动作发生于过去，英语中情态动词后加动词的完成式表示对过去动作的猜测，故选D。C项意为“本来应该掉出来”，不合题意。

查看本题答案和解析