The answer is D. Defence.
The other four words (raid, attack, assault, and ambush) all refer to an act of violence or aggression against another person or group. Defence, on the other hand, refers to the act of protecting oneself or another from attack.
A raid is a sudden attack on a place, usually carried out by a small group of people. An attack is a violent act against another person or group. An assault is a violent attack that is intended to cause serious injury or death. An ambush is a surprise attack on an enemy, usually carried out from a concealed position.
Defence is the act of protecting oneself or another from attack. It can be done through a variety of means, such as physical force, weapons, or fortifications. Defence can also be done through diplomacy or other means of resolving conflict without violence.