Why Do States Usually Try to Solve Their Disagreements Through

Why do states usually try to solve their disagreements through bargaining?

A) War is a costly option that states would rather avoid if possible.
B) States use the negotiation period to prepare surprise attacks against their opponents.
C) International institutions force states to negotiate.
D) Bargaining usually results in the best result for all of the actors who are involved in a dispute.
E) Negotiating with other states is the only way to achieve a state's goals.