Since nobody gave him any help, he have done the research on his own.
A. can
B. must
C. would
D. Need
网友回答
A. can
(答案→)B. must
C. would
D. Need
解析：考查情态动词和虚拟语气。can have done sth可能已经做了某事；must have done sth一定已经做了某事；would have done表示与过去的事实相反；need have done sth本来需要做某事。句意“因为没有人给他任何的帮助，他一定是自己完成的那项，研究。”根据，句意可知，表示的是肯定的推测，用must，故选B。
【考点定位】情态动词和虚拟语气。