In which subject class of the Dewey decimal system would you find mark twain's Huckleberry Finn A 000-099 B 300-399 c 800-899 b 600-699?

The Dewey decimal system is really only used for non-fiction books, and since Huckleberry Finn is fiction, it wouldn't be represented. Your best bet is to just look in the fiction section under "T" for Twain, Mark.