The man called his professor for help because he couldn’t solve the problem by .A. herself

问题补充：

The man called his professor for help because he couldn’t solve the problem by .

A. herself

B. himself

C. yourself

D. themselves

答案：

A. herself

(答案→)B. himself

C. yourself

D. themselves

解析：herself她自己；himself 他自己；yourself你们自己，你自己；themselves他们自己。句意：这个人向他的教授请求帮助，因为他不能独自解决这个问题。结合语境可知下文反身代词指代的是前文的the man，男性，单数，故选B。