— Catherine, I have cleaned the room for you.
— Thanks. You it. I could manage it myself.
A. needn’t do
B. needn’t have done
C. mustn’t do
D. shouldn’t have done
网友回答
A. needn’t do
(答案→)B. needn’t have done
C. mustn’t do
D. shouldn’t have done
解析：根据句意可知Catherine对对方为她打扫了房间表示感谢并提到对方本来不必为她打扫房间。很显然对方打扫房间是过去所为，表达“去不必做某事”用needn’t have done sth.