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.
(A)Marconi's conception of the radio was as a substitute for the telephone, a tool for private conversation; instead, it is
(B)Marconi conceived of the radio as a substitute for the telephone, a tool for private conversation, but which is
(C)Marconi conceived of the radio as a tool for private conversation that could substitute for the telephone; instead, it has become
(D)Marconi conceived of the radio to be a tool for private conversation, a substitute for the telephone, which has become
(E)Marconi conceived of the radio to be a substitute for the telephone, a tool for private conversation, other than what it is,
题目分析：句子表达了radio以前是当做什么用的现在当什么用的。进行了强对比，如果用which is或者other than就无法体现这种强对比了，我们干掉BDE。AC进行比较，一个用conception一个用conceived，后面都用了it，根据意思我们知道it应该指代radio，如果前面用conception，后面用instead it，it就可能指的是conception了，如果改成动词，it指代不了动词，只可以只radio了，选C
