An author may quote a source to preserve the narrative language, maintain the distinction between the source's voice and their own, or to avoid inaccuracies that could arise from paraphrasing. Hence the correct option is C.
The most likely reason an author would quote a source rather than paraphrasing it is to preserve the narrative language, to distinguish the source's voice from their own, or to avoid introducing inaccuracies. Authors may choose to quote directly when the exact wording of the source is important for maintaining the original emphasis or tone or when the words chosen by the original author are particularly striking or authoritative.
This can serve to make an argument more compelling or to ensure that specific, nuanced points are conveyed accurately. Quoting also helps to prevent any potential distortion that might occur with paraphrasing if the original meaning or context could be lost.
Hence the correct option is C.