--- Catherine, I have cleaned the room for you.--- Thanks. You ________ it. I could manage it myself.A.needn't doB.needn't have doneC.mustn't doD.shouldn't have done
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B解析needn't do"不必做"；needn't have done"本不必做某事 (实际上已经做了) "；mustn't do"不准做"，表禁止、命令；shouldn't have done"本不应该做 (实际上已经做了)"。