【题目】 I ______ have worried before I came to the new school, for my classmates here are very friendly to me.
A.mightn't
B.mustn't
C.needn't
D.couldn't

【答案】C
【解析】句意：我来新学校之前本没有必要担心，因为在这里我的同学对我非常友好。needn't have done 本没有必要做某事，表示实际上已经做了某事。根据句意可知选C。