Final answer:
The correct term describing the involvement of multiple parties in public sector collective bargaining is 'Multilateral bargaining'. This form of bargaining includes a range of stakeholders due to the public nature of the sector.
Step-by-step explanation:
The labor relations term used to describe the involvement of multiple parties in the collective bargaining process, particularly at the state and local level public sector bargaining, is d. Multilateral bargaining. Multilateral bargaining involves many participants beyond the traditional two parties—employer and union—that dominate the private sector negotiations. Public sector bargaining can involve a more complex array of stakeholders, including various government agencies, elected officials, and sometimes the general public due to the nature of public accountability and funding.