GWD31-23-19

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

key is E, why use to be,what is wrong with B?thanks