The correct answer is D. delicate.
Peacekeeping is a delicate task because it involves dealing with complex political and social issues. Peacekeepers must be able to build trust and relationships with all parties involved in a conflict, and they must be able to operate in a difficult and dangerous environment.
The other options are not as accurate descriptions of peacekeeping. Laborious means requiring a lot of physical effort, and inconvenient means causing trouble or difficulty. Difficult means hard to do or understand, but it does not capture the complexity of peacekeeping.