Alyssa thinks that her company is discriminating against a particular group of employees by denying them seniority or promotions. She expresses her concern to a senior human resources manager. This method of expressing concern about an instance of illegal employment through proper channels is known as .

Opposition  

Explanation:

  According to the given question, Alyssa is working in an organization and she thinks that an organization are discriminating the specific group of the employees by the process of deny the various types of employee's promotions.

The opposition is one of the type of method that helps in expressing the concern about the given concept of the illegal employment and it is one of the process of disagreement with the given situation in the company.

 Therefore, Opposition is the correct answer.