Her parents______her letter last week. They dont know what has happened to A．must receive B．must have received C．ought to receive D．ought to have received
A.must B.must C.ought D.ought
【参考答案】
D 本题考查情态动词，根据题意，他的父母本该上周就收到她的信，他们不知道她出了什么事；可以知道是对过去本该发生而......