Which of the following actions could be considered retaliation?

Retaliation occurs when an employer takes adverse action against an employee for engaging in protected activities, such as filing a discrimination complaint. Firing an employee after they have made such a complaint is a clear example of retaliation, as it suggests that the employer is penalizing the employee for standing up for their rights or for raising concerns about discriminatory practices.

In contrast, the other actions mentioned do not reflect retaliation. Offering promotions based on performance, providing training opportunities, and allowing flexible work hours are all practices that can contribute positively to an employee’s work environment and development. These options typically do not involve any negative consequences potentially tied to an employee's previous complaints or claims. Thus, they do not exemplify retaliatory behavior, which is specifically characterized by negative actions taken in response to protected activities.