COMBAT

Answer: Option D

Conflict : a serious disagreement or argument, typically a protracted one.
Quarrel : a heated argument or disagreement, typically about a trivial issue and between people who are usually on good term.
Feud : a prolonged and bitter quarrel or dispute.
Fight : take part in a violent struggle involving the exchange of physical blows or the use of weapons.
Combat : fighting between armed forces.


Synonym of Combat is Fight