The CDs are on sale!Buy one and you will getcompletely for freeA. itB. othersC. thatD. on

问题补充：

The CDs are on sale!Buy one and you will getcompletely for free．

A. it

B. others

C. that

D. one

答案：

A. it

B. others

C. that

(答案→)D. one

解析：句意：这个光盘正在促销！买一赠一。It和that都指已经提到过的事物；others指其余的；这里表示泛指的任何一个，故用one，选D。