Cool! Perhaps you could sort the answers alphabetically so that when people get stuck they can get a hint by seeing the positioning of the missing answers?
Surprised to see 'hmm', 'huh' and 'ooh' in the list!
OK, we've taken out the four exclamations (hmm, huh, ooh and wow). Leaving it in frequency order is trickier as you say, but there's lots of time to get them, and it will be interesting to see how closely the percentage guessing an answer follows the rank frequency of that word.
Surprised to see 'hmm', 'huh' and 'ooh' in the list!