题目内容：

He can't find his key.He ---------- them.A.must lost B.must have been lost C.must have lost

优质解答

He can't find his key.He ---C------- them.A.must lost B.must have been lost C.must have lostmust have done表推测已经发生的事情,“一定已经做过某事”A 错误 应该是must +动词原形B 错误 must have been lost...