This scenario best demonstrates negative automatic reinforcement.
Explanation: Elton is feeling disappointed in himself for skipping his workouts, which serves as an internal negative consequence for not exercising. His determination to show up for all his workouts next week indicates he is motivated to change his behavior to avoid that negative feeling again, which aligns with the concept of negative automatic reinforcement, where the removal of a negative feeling (disappointment) reinforces the desired behavior (working out).