GMAT Sentence Correction (SC) | Marconi's conception of the radio was as a substitute for th

Marconi’s conception of the radio was as a substitute for the telephone, a tool for private conversation; instead, itis[/u] 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 - conception of is unidiomatic; Use of simple present tense is incorrect as the change happened over a course of time . We need present perfect .
B. Marconi conceived
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