一How dangerous it was!
—Yes，but for the young man’s quick action，he run over by the car．
A. must have been
B. could have been
C. would be
D. might be
网友回答
A. must have been
(答案→)B. could have been
C. would be
D. might be
解析：句意：--这多危险啊！--是的，要不是这个年轻人的迅速行动，他就被汽车撞到了。but for “要不是”，相当于一个虚拟条件句，因为是和过去相反的动作，所以主句用would/Could/might have done,所以选B。