有一道情态动词的题目,There were already five people in the car but

题目

有一道情态动词的题目,There were already five people in the car but
-There were already five people in the car but they managed to take me as well.
-It______a comfortable journey.
A,can't be
B,shouldn't be
C,mustn't have been
D,couldn't have been
我选的C 想着这是表过去的推测 D 为什么?学校发的讲义上解释couldn't have been为本能够做某事却没做.带进去语意很奇怪啊.这两个怎么区分啊.

答案

这里的couldn't have been其实是can't have been.没有mustn't have done 这种说法哦,在用否定的推测时只能用can 或者could,这里的could等于can,应该是让语气更委婉吧