You the work better, but you didn’t put more efforts to it.
A. must have done
B. can have done
C. should have
D. could have done
网友回答
A. must have done
B. can have done
C. should have
(答案→)D. could have done
解析：考查虚拟语气。句意：你本可以做得更好，但是你没有付诸更多的努力。could have done本可以做某事；must have done sth一定已经做了某事；should have done sth本应该做某事（实际上未做）。故选D。