Final answer:
Melinda's mindset of evaluating her achievements, actions, and identity based on her comparison with her best friend Stacy is an example of social comparison.
Step-by-step explanation:
The correct answer is a) social comparison. Melinda's mindset of evaluating her achievements, actions, and identity based on her comparison with her best friend Stacy is an example of social comparison. Social comparison is the process by which individuals evaluate themselves by comparing their abilities, attributes, and achievements to others.