----Could you please come to the museum with me this afternoon?----Sorry,I____.I have to take a piano lesson at 2:00 pm.A couldn't B mustn't C can't D needn't 选择 带上理由
问题描述：
----Could you please come to the museum with me this afternoon?
----Sorry,I____.I have to take a piano lesson at 2:00 pm.
A couldn't B mustn't C can't D needn't 选择 带上理由
答
选C（can't).
理由：问句是COULD表示委婉,但回答时需要用can表示实际情况,不需要对自己委婉.另外A,也是过去式.不能使用.没有B的用法,D的意思是,不必要.
所以,只能先C.