Final answer:
The mood adjective 'optimistic' is correctly defined as 'B. Hopeful', meaning having a positive outlook and expecting the best possible outcomes.
Step-by-step explanation:
The correct definition for the mood adjective optimistic is B. Hopeful. Being optimistic means having a positive outlook and expecting the best possible outcome in a given situation. It involves a belief that good things will happen and that goals can be achieved. This is contrary to being pessimistic, which would involve expecting the worst.