问题
选择题
.We were all waiting for you .You _____for the seaside by yourself without leaving a message.
A．mustn’t leave
B．shouldn’t have left
C．couldn’t have left
D．needn’t leave
答案
答案：B
这是情态动词的特殊用法，shouldn’t have left表示本来不应该做但实际已经做了。