True or false with short explanation

The demand for emergency medical services is elastic.

The market demand curve is made up from individual demand curves.

Self-regarding preferences usually are concerned with the material well-being of others.

Other-regarding preferences have elements of concern for the material well-being of the decision maker and the material welfare of others as well.

Choice is a key component of economic theory.

National defense is an example of a public good.

Market failure is a situation where the market fails to use resources efficiently.