Five minutes earlier,and we___the last subway train

题目

Five minutes earlier,and we___the last subway train
ought to have caught must have caught could have caught could catch
选什么为什么

答案

could have caught
虚拟语气,
再早五分钟,我们就赶上最后一趟地铁了.
事实上没能赶上.
A不行,不是应该,而不能不能的问题.