Answer:
C) conciliation
Step-by-step explanation:
When a neutral third party gets involved in a collective bargaining dispute involving unions, it can be either a mediator or conciliator depending on the stage of the negotiations.
In this case, since the problem hasn't escalated yet to a strike or or a lockout, the third party involved is a conciliator. Generally a conciliator is called to help the company and the union to reach an agreement before things get complicated.
If the conciliator is not successful, and things start to get messy, then you have to call a mediator. Which can actually be the same person, but just as a medical examiner is a doctor that looks at dead people while a MD treats living people, a mediator gets involved once the fight starts while the conciliator tries to avoid it.