Sentence Correction

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,

OA: C

IMO: C

"conceived of X as Y" is a pattern
then A.D and E are out.. between B and C also, choice C convey its message more accurate..

This is an OG 12 Question.

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.

Let's choose which of the GMAT errors the sentence has:
1. Rhetorical Construction
2. Parallelism
3. Diction
4. Verb Form
5. Agreement
6. Grammatical Construction
7. Logical Predication
8. Idiom

LOGICAL PREDICATION, RHETORICAL CONSTRUCTION
'Marconi's Conception of' is an awkward usage it might have been right if it was 'Marconis conception that'.

Let's see each answer choice.

A) Marconi's conception of the radio was as a substitute for the telephone, a tool for private conversation; instead, it is - INCORRECT Marconi's conception of is wrong. Also the subject here becomes Marconi's concetion not the radio and is referred by later clause as a tool for private conversation. Marconis conception was not the tool instead the radio was.
B) Marconi conceived of the radio as a substitute for the telephone, a tool for private conversation, but which is - INCORRECT From experience i have seen 'which' usage is very doubtful in most of the answer choices. It is used to introduce a non restrictive clause (a clause which is not important in the sentence) and it is a relative pronoun which should immediately follow its referent. Here it seems to refer to 'a tool for private conversation' when it should actually be referring to Radio which it describes in the clause that follows.
C) Marconi conceived of the radio as a tool for private conversation that could substitute for the telephone; instead, it has become - CORRECT - First clause is completely error free, semi colon introduces a second clause which has 'it' referring clearly to radio of the first clause.
D) Marconi conceived of the radio to be a tool for private conversation, a substitute for the telephone, which has become - INCORRECT - 'Conceived of the radio' should be followed by 'as'. Which is a relative pronoun which should immediately follow its referent. Here it refers to telephone clearly and not radio.
E) Marconi conceived of the radio to be a substitute for the telephone, a tool for private conversation, other than what it is, INCORRECT - 'Conceived of the radio' should be followed by 'as'. Also 'other than than what it is' is awkward.

Takeaway:
1. Think twice when 'which' appears in a sentence. It has to comply to the following to be correct:
The relative pronoun which should immediately follow its referent. It introduces non restrictive clauses, which include information relevant, but not critical to an understanding of the sentence.
2. IDIOM - Conceived of X as Y.

heres how i did this without using idioms (coz i cudnt remember it)

the sentence means a dude named Marconi viewed the telephone as a device for private communication like the telephone was (and that it could replace the telephone as well).. but instead it turns out that the radio did just the opposite (it was used for public communication)

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 --> i removed this in the end after comparing it with C which said that the radio instead became into smth else AFTER marconi's conception
B) Marconi conceived of the radio as a substitute for the telephone, a tool for private conversation, but which is --> which modifies conversation
C) Marconi conceived of the radio as a tool for private conversation that could substitute for the telephone; instead, it has become --> kept this (turns out it was right)
D) Marconi conceived of the radio to be a tool for private conversation, a substitute for the telephone, which has become --> a substitute modifies private conversation
E) Marconi conceived of the radio to be a substitute for the telephone, a tool for private conversation, other than what it is, --> 'it' refers to???

so i took C...
also notice that C keeps the sentence together... "precisely the opposite, a tool for communication with a large, public audience" ... is clearly in contrast with ".. the radio as a tool for private conversation" ... which is the main point... (the substitution is not the main point)

IMO C

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 - PASSIVE
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,

imo: c