Since nobody gave him any help, he have done the research on his own. A．can B．mu

Since nobody gave him any help, he    havedone the research on his own.

A．can              B．must             C．would            D．Need

试题答案

【答案】

B

【解析】考查情态动词和虚拟语气。canhave 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；needhave 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。