Luis is five years old and tries to dress and talk like his father, whom he admires. this makes him feel "grown-up" and invincible. luis is exhibiting which defense mechanism?

Luis is exhibiting the defense mechanism of identification. When a person uses identification, they are attempting to personify the 'good' or admirable traits of another person in order to make up for the negative traits (or perceived negative traits) in themselves. Here, Luis is doing exactly that by talking like his father.