This kind of CD-ROM is very popular. Why not buy one before it?A. comes out B is come out

问题补充：

This kind of CD-ROM is very popular. Why not buy one before it?

A. comes out B is come out C. is sold out D. sells out

答案：

解析：根据上下文的内容，本题选用的内容为sell out表示卖完的意思，相当于及物动词，可以有被动语态，故选答案为C