Option 1 -> Hostile means showing aggression or antagonism, directly matching the meaning of belligerent.
Option 2 -> Hostage refers to a person held captive, completely unrelated to belligerent.
Option 3 -> Enemy is a noun for an opponent, not an adjective describing aggressive behavior.
Option 4 -> Unfriendly is too mild; belligerent implies active aggression, not just a lack of friendliness.
Hence, Option 1: Hostile -> Both "belligerent" and "hostile" describe an aggressive, confrontational, and combative attitude or behavior, making them true synonyms -> correct