---Are these your books?Yes .A. I amB. these areC. they areD. you are

问题补充：

---Are these your books?

--- Yes, .

A. I am

B. these are

C. they are

D. you are

答案：

A. I am

B. these are

(答案→)C. they are

D. you are

解析：固定短语are these…?的肯定性答语是yes，they are。否定性答语是no,they aren’t.故选C.