单项选择题

My wallet is nowhere to be found; ______ while I was on the bus.

A．should I dropped it
B．I must have dropped it
C．I ought to have dropped it
D．I had been dropping

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It was (consider) ______ of you not to play the piano while I had a bad toothache.

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Why did Mr. Richards’ relatives prefer to stay in his houseBecause they might ______.