of them knows the answer. What can we do now?- Let’s ask a third boy for help.A. B

问题补充：

--- of them knows the answer. What can we do now? --- Let’s ask a third boy for help.

A. Both

B. Either

C. Neither

D. None

答案：

A. Both

B. Either

(答案→)C. Neither

D. None

解析：根据Let’s ask a third boy for help.可知，前面是两个人，并且两个都不知道答案，故应该用C。Both“两者都”，either“两者中的一个”，neither“两者不”，none“都不（三者以上）。所以本题选C。