Final answer:
A b)mediator is needed to de-escalate a case by helping parties in a conflict reach a mutually acceptable resolution.
Step-by-step explanation:
The role needed to de-escalate a case is a mediator. A mediator is a neutral third party who helps parties in a conflict reach a mutually acceptable resolution. They facilitate communication and promote understanding between the parties involved. For example, in a conflict between two individuals, a mediator would listen to each person's perspective, help them articulate their needs and interests, and guide them towards finding a peaceful resolution.