6240. War was not the only inevitable means to decide that dispute.

✅ The correct answer is option C.
Indefinite : lasting for an unknown or unstated length of time.

Imminent : about to happen.

Unavoidable : not able to be avoided, prevented, or ignored; inevitable.

Improbable : not likely to be true or to happen.

Inevitable : certain to happen; unavoidable.

Synonym of Inevitable is Unavoidable