Which term describes someone who is combative or aggressive?

The term that describes someone who is combative or aggressive is "belligerent." This word originates from the Latin "bellum," meaning war, and it is often used to characterize individuals who exhibit a willingness to engage in conflict or hostility. A belligerent person may be confrontational and ready to argue or fight, reflecting a tendency toward aggression in their demeanor or actions.

In contrast, the other terms provided do not convey this aggressive quality. "Submissive" refers to a tendency to yield or submit to the authority or control of others, which is the opposite of combative behavior. "Tranquil" signifies a state of peace and calmness, indicating a lack of aggression or conflict. Similarly, "serene" denotes a state of being calm and untroubled, further distancing itself from the notion of combative behavior. Thus, "belligerent" is the only term in this context that accurately captures the essence of someone who is aggressive or combative.