Explanation:

- The given process involves mediation to reach an agreement between workmen and employers.

- Option 1: Arbitration - Involves a third party making a binding decision, rather than facilitating mutual agreement.

- Option 2: Adjudication - Refers to a formal judgment, usually by a legal authority, rather than a mediated agreement.

- Option 3: Conciliation - Correct. This process involves a conciliator who mediates between parties to facilitate a mutually satisfactory agreement.

- Option 4: Collective negotiation - Refers to bargaining between employers and a group of employees, typically without a mediator.