问题
选择题
— 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
答案
答案：B
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.