6548. Peace keeping for the United Nations is, at best of times and arduous task.

✅ The correct answer is option C.
Laborious : requiring considerable time and effort.

Inconvenient : causing trouble, difficulties, or discomfort.

Difficult : needing much effort or skill to accomplish, deal with, or understand.

Delicate : very fine in texture or structure; of intricate workmanship or quality.

Arduous : involving or requiring strenuous effort; difficult and tiring.

Synonym of Arduous is Difficult