(A) and (B) are natural, (C) is not really. They mean the same thing (near enough) but I would be very surprised to hear any native speaker use (C). People call a flower something rather than name a flower something.
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AnonymousC might be used in American English because speakers of that usually say named instead of called.I don't know where you got that from. Google Ngrams is unable to find any examples of "what is it named" either in American English or in British English.