问个分号的问题

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,

答案是C，但我觉得分号应该是个独立的句子，不应该在用连词instead,哪位大虾能解释下

这个题不用看分号。

1，conceive as

2，which的指代搞清

3，tool做同位语，不能放在telephone后面。逻辑意思不对。

你说的这些我都知道，我想问的就是关于分号的用法，因为分号应该也是ets的考点之一。

So，哪位大虾能否就该题讲一下分号的用法，即为什么该题中分号不受影响。