-- behind the door?--No they arent.A. Where areB. WhatsC. Are those keysD. Is the key

问题补充：

-- behind the door?

--No, they aren .

A. Where are

B. Whats

C. Are those keys

D. Is the key

答案：

A. Where are

B. Whats

(答案→)C. Are those keys

D. Is the key

解析：根据答语可知问句是一般疑问句，又因答语中的代词是they，可知问句中的名词是复数形式，故选C。