--Are you going to buy a new camera?--Yes. But there are so many cameras that I cant deci

问题补充：

--Are you going to buy a new camera?

--Yes. But there are so many cameras that I can decide

A. how to use B. where to sell C. which to buy

答案：

解析：how to use如何用；where to sell哪去卖；which to buy买哪一个；句意：你打算买一部新的照相机吗?——是的，但是这儿有如此多的照相机，以至于我不能决定买哪一个。结合语句可知选C。