Realist theories were formulated in the post-Second World War era, influenced by the idea that idealist theories failed since they proved unsuccessful in preventing or even foreseeing another world war. Therefore, according to the realist theory, the way to prevent wars was not moral values or international institutions but balance of power in the international system. Although the state is the main actor in realist theory, it is also attributed features from human nature. But human nature does not have positive connotations like it has in the idealist theories. The correct answer is C.