This is true. When you choose between two things, the thing that you didn't choose is what cost you the thing you chose. It's called an opportunity cost and it presents what you had to lose or give up in order to attain the thing that you chose and assessing these costs is extremely important in decision making.
B) to prevent war. The United Nations was supposed to do that after World War II, as the League of Nations was ineffective at it.
Because Societies located in the same region can affect each other's development.
