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题目内容
（郑州工程技术学院-建筑CAD）
My wallet is nowhere to be found.I_____it when I was on the bus.
(A) must drop
(B) should have dropped
(C) had dropped
(D) must have dropped
(A) must drop
(B) should have dropped
(C) had dropped
(D) must have dropped
参考答案