Question

collective bargaining means bargaining with workers who strike individually. debate regularly. refuse to join unions. belong to a union.

Explanation:

Collective bargaining involves negotiations between employers and a group of employees (usually represented by a union). Workers who strike individually are not part of collective bargaining. Regular debate is not the essence of collective bargaining. Workers who refuse to join unions are not in a collective (union - represented) group. Collective bargaining is about bargaining with workers in a union.

Answer:

belong to a union.