We live the second floor a flat.A. at; inB. on; atC. on; inD. in; on

问题补充：

We live the second floor a flat.

A. at; in

B. on; at

C. on; in

D. in; on

答案：

A. at; in

B. on; at

(答案→)C. on; in

D. in; on

解析：句意：我们住在一个公寓的二楼上，在···公寓内，用in,在第几层楼用on，故选C