My opponent has chosen rock in 4 out of 8 rounds, including the most recent round. There's a reasonable chance they'll choose rock again to continue their winning streak. Additionally, they may expect me to choose rock to break the pattern of my recent losses, which would lead them to choose paper. By choosing paper, I can beat rock and tie against paper, giving me the best statistical chance in this situation. This is a critical round as we're tied 3-3 with only two rounds remaining.