Q19:

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,

请问E中的it is 指代什么东东呢

这题选C啊 concieve of sth as sth

E错的原因也包括what it is 表达不清啊