Help！ Gmat语法

Marconi’s conception of the radio was as a substitute for the telephone, a tool for private conversation; instead, it is precisely the opposite, a tool for communicating with a large, public audience.

1. Marconi’s conception of the radio was as a substitute for the telephone, a tool for private conversation; instead, it is
               
2. Marconi conceived of the radio as a substitute for the telephone, a tool for private conversation, but which is
               
3. Marconi conceived of the radio as a tool for private conversation that could substitute for the telephone; instead, it has become
               
4. Marconi conceived of the radio to be a tool for private conversation, a substitute for the telephone, which has become
               
5. Marconi conceived of the radio to be a substitute for the telephone, a tool for private conversation, other than what it is,

请NN帮忙解答！ 谢

support D

我是这么想的 

conceive to be> conception

which 就近修饰telephone

当然我是马后炮，以前看过别人的讨论，个人觉得D 好一些吧