【一道关于情态动词的英语习题Thehadplentyofbread,soshe__aloaf.A.needednottobuyB,neednottohaveboughtC,needn'thaveboughtD.didn'tneedtobuy这道题应该怎么判断选哪个?如何判断need是做情态动词还是实义】

　　一道关于情态动词的英语习题

　　Thehadplentyofbread,soshe__aloaf.

　　A.needednottobuyB,neednottohaveboughtC,needn'thaveboughtD.didn'tneedtobuy这道题应该怎么判断选哪个?如何判断need是做情态动词还是实义动词呢?如果做实义动词那么D的用法对吗?可以说是didn'tneed吗