Have you returned the book to him ? Yes I have returned it.A. yet yetB. already already

问题补充：

Have you returned the book to him ? Yes, I have returned it.

A. yet, yet

B. already, already

C. yet, already

D. already, yet

答案：

A. yet, yet

B. already, already

(答案→)C. yet, already

D. already, yet

解析：yet和already都可以表示已经，还得意思，却别是前者用于疑问及否定句当中，后者用于肯定句当中。结合语境可知前文是疑问句，下文是否定句，故选C。