Final answer:
d) It is nonrival in consumption and nonexcludable. A public good is nonexcludable and nonrivalrous, meaning it cannot be excluded from anyone and does not prevent others from using it. An example is national defense.
Step-by-step explanation:
A public good is a good that is nonexcludable and nonrivalrous. Nonexcludable means that it is costly or impossible to exclude someone from using the good. Nonrivalrous means that when one person uses the good, it does not prevent others from using it. An example of a public good is national defense. If national defense is being provided, it includes everyone and cannot be excluded from anyone.