问题
选择题
They have arrived at lunchtime, but their flight was delayed.
A．will
B．can
C．must
D．should
答案
答案：D
考查虚拟语气。根据后一句their flight was delayed.可知这是对过去情况进行假设。Must have done一定做了某事（表示推测）；should have done本应该做某事实际上却没有做。句意：他们本应该在午饭到，但是他们的航班延误了！