—How did it that you made such a silly mistake?—I myself haven’t figured it out yet.A. b

问题补充：

—How did it that you made such a silly mistake?

—I myself haven’t figured it out yet.

A. bring about

B. come about

C. come across

D. come on

答案：

A. bring about

(答案→)B. come about

C. come across

D. come on

解析：句意为：--你做出这么愚蠢的决定，怎么会发生这种事儿呢？--我自己也弄不明白（怎么会发生这种事情）。bring about 引起，使掉头；come about产生，发生；come across（偶然）遇到，碰到；come on加油，快点，开始。故答案为B