I such a foolish mistake if I had been a little more careful.
A. wouldn’t make
B. wouldn’t have made
C. hadn’t made
D. didn’t make
网友回答
A. wouldn’t make
(答案→)B. wouldn’t have made
C. hadn’t made
D. didn’t make
解析：这道题是一个与过去事实相反的虚拟语气，if条件从句用的是过去完成时态，主句应用would have done 结构。因此答案选B.