Answer:
Option D, done to protect against an attack, is the right answer.
Explanation:
In simple term, defensive war is a kind of war which is employed in defense to a war.
A defense war is a war where at least one nation is trying to defend itself from the attack of another nation. It is not a kind of war where both nations try to invade and establish their control over each other. The war of 1812 by the Americans against the Britishers is often seen as a defensive war.
