My wallet is nowhere to be found. I ____ when I was on the bus. （QE96-36）
A、must have dropped it
B、must drop it
C、should have dropped it
D、ought to have dropped it
【正确答案】：A
【题目解析】：本题测试情态动词。“must have done”表示对已发生的事情进行肯定推测。本句的意思是：“我的钱包找不到了。我一定是在公共汽车上掉的。” should have done/ ought to have done 表示的是应该做却没有做的事
