The impact of Keats's repetition of the word "what" is that it emphasizes the curious tone of the speaker. Option C is correct.
Repetition helps emphasize the point to the audience. The audience is more likely to remember something that has been repeated. Repetition is a literary device that repeats the same words or phrases a few times to make an idea clearer and more memorable. it may be a word, a phrase, or a full sentence, or a poetical line repeated to highlight its significance in the entire text.