He had known the matter before you told him, so you____ have tol

He had known the matter before you told him, so you____ have told it to him.
A、mustn't
B、can't
C、needn't
D、shouldn't
【正确答案】：C
【题目解析】：【考点点击】本题考查情态动词。【要点透析】 must have done表示肯定推测,意为“过去一定做过某事”,没有 mustn't have done的说法;can''tcouldn't' have done为否定推测,意为“不可能做了某事”; needn't' have done意为“不必要做某事(而做了); shouldn't' have done意为“本不应做某事(而做了)”。本句意为:他已经知道了此事,你不必再告诉他了(实际上已经告诉他了)。故为C。