---Have you returned the book to the library ? -Yes I have returned it.A. yet yet B.

问题补充：

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

A. yet, yet

B. already, already

C. already, yet

D. yet, already

答案：

A. yet, yet

B. already, already

C. already, yet

(答案→)D. yet, already

解析：yet和already都表示 “已经”之意，通常用于完成时态。yet 用于问句或否定句，位于句尾；而 already 用在肯定句里，位于句中，即be动词或助动词之后，行为动词之前。故本题选D。