Explanation:

- Option 1: White-collar union – Correct Answer. These unions protect the rights and interests of non-manual employees. White-collar workers are typically those who do office jobs, administrative work, management, or professional roles.

- Option 2: Blue-collar union – These unions are meant for manual workers, such as factory workers, technicians, or anyone who performs physical labor.

- Option 3: Brown-collar union – This term is not commonly used or recognized for unions or employee categories.

- Option 4: None of the above – Not correct, as option 1 is the answer.