The correct answer is B. Collective bargaining.
Collective bargaining is the process of negotiation between employers and the representatives of a unit of employees aimed at reaching agreements that regulate working conditions. These agreements usually cover issues such as wages, hours, and working conditions.
Participation management is a process that involves employees in decision-making. This can be done through a variety of methods, such as team-based work, quality circles, and employee surveys.
A code of conduct is a set of rules that employees are expected to follow. These rules can cover issues such as ethics, safety, and discrimination.
None of these options is the process of negotiation between employers and the representatives of a unit of employees aimed at reaching agreements that regulate working conditions.