Looking at the opponent’s past moves, a pattern can be discerned: rounds 3 and 6 were both scissors, and since rounds 3, 6, and possibly 9 might align (every third round being scissors), it’s plausible that round 9 will be scissors as well. Additionally, a frequency count shows that the opponent has used paper and rock three times each and scissors only twice so far; to balance this out, he might choose scissors in round 9. Since rock beats scissors, I'll choose rock for this round.