真题练习

817.He paid for a seat,however,he ________ have entered free.

A.could
B.would
C.must
D.need

818.Helen _______ go on the trip with us,but she isn't quite sure yet.

A.shall
B.must
C.may
D.can

答案解析

817.答案是A;paid暗示时间上指的是过去，could have done表示本可以做而没有做的事情。
818.答案是C;根据下文but she isn't quite sure yet得知，此处说话人把握不大，故选用may也许，有可能。