—Is the letter from your mother? —Yes. B

问题选择题

—Is the letter from your mother?

—Yes. But she ________ the letter herself, because she doesn't even know one word.

A．needn't have written

B．can't have written

C．might not have written

D．should not have written

答案

答案：B

选B　考查情态动词。句意：“这封信是你母亲来的吧？”“是的。但这封信不可能是她自己写的，因为她一个字也不认识。”根据because引导的原因状语从句可知，此处应用can't have done表示对过去发生的事很有把握的否定推测。