Why Is It Important to Examine the Interests of State

Why is it important to examine the interests of state leaders when attempting to explain the likelihood of war?

A) State leaders are usually put in place by the military,thus their interests are crucial to a declaration of war.
B) The public needs to know what those interests are before an election,so they can elect a good leader,since there is no way to influence the leader's decisions after an election.
C) The likelihood of war decreases as the age of a leader increases.
D) Leaders have the authority to make foreign policy decisions,even if other actors influence them.