Question

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

A．can

B．must

C．would

D．Need

Answer 1

B

考查情態(tài)動(dòng)詞和虛擬語(yǔ)氣。can have done sth可能已經(jīng)做了某事；must have done sth一定已經(jīng)做了某事；would have done表示與過(guò)去的事實(shí)相反；need have done sth本來(lái)需要做某事。句意“因?yàn)闆](méi)有人給他任何的幫助，他一定是自己完成的那項(xiàng)，研究�！备鶕�(jù)，句意可知，表示的是肯定的推測(cè)，用must，故選B。
【考點(diǎn)定位】情態(tài)動(dòng)詞和虛擬語(yǔ)氣。