How can an architect achieve this requirement?

Universal Containers (UC) has implemented Service Cloud. There is a flag field on the case object that marks a case as (Sensitive). UC requested that this flag can be viewed by all users who have access to the case but only be edited by the assigned case assessor. The case assessor is a lookup field on the case object.

How can an architect achieve this requirement?
A . Permission Set.
B. Object Permissions.
C. Custom Lightning Component.
D. Field-level security

Answer: C