By serving others，a person focuses on someone other than himself or herself， can be very eyeopening and rewarding.
A. who
B. which
C. what
D. that
网友回答
A. who
(答案→)B. which
C. what
D. that
解析：后面一句是非限制性定语从句，从句缺少的是主语，先行词是前面整句话的内容，所以用which引导。句意：通过为别人服务，一个人就会关注某人而不是他/她自己，这样也许就能使眼界非常开阔并获得回报。