Collective bargaining involves; A.employers only B.workers and employer C.workers only D.workers' representative and employer

When dealing with unions the answer is D. 

However if your company isn't unionized then it is A.  Employees will organize themselves to negotiate wages and other conditions of employment. 

(At least in the States its like that, not sure how it is in ME) 

Option D

D Option :)

The answer is correctly mentioned by my colleagues(D)