The primary purpose of collective bargaining is to

A. ensure worker participation in setting the goals and objectives of the company.

B. establish and communicate clear guidelines for performance appraisals.

C. limit the authority of management to set job categories and direct worker activities.

D. negotiate a labor-management agreement that both the union and management are willing to accept.

The ones in bold are ones that are confusing me. Which one is the correct answer? Please tell me the answer and explanation.