The phrase ‘word-for-word’ means to follow the exact order of words while speaking or reciting something. This is a common idiomatic phrase that is used to speak about recitation. In the given context the person repeats the other person’s words without changing the order of things. Hence the preposition ‘for’ is the suitable option since it conveys the same. Thus option C is correct. Whereas prepositions ‘at’, ‘to’ and ‘after’ cannot be placed between the two words to form any coherent sense or meaning. Thus options A, B, and D are incorrect.