A good is excludable if: a) Those who are unwilling or unable to pay for the good do not obtain its benefits. b) It is not possible to prevent an individual from using the good. c) The quantity of the good is affected by the price a consumer pays for the good. d) Consumption of the good by one person decreases the ability of other people to consume the good.

The correct answer is letter "A": Those who are unwilling or unable to pay for the good do not obtain its benefits.

Explanation:

The excludability feature of goods does not allow individuals to have access to them without having paid for them. Thus, non-excludable goods are those that no one cannot prevent its use. Private goods (clothing, vehicles, houses) are excludable but they are also considered rival goods since when one person uses it another individual cannot consume the goods.