Which of the following is an example of a public good?

• A. National defense
• B. A slice of pizza
• C. A private swimming pool
• D. A toll road

Answer: (A)

Verified step by step guidance

1. Understand the definition of a public good: it is a good that is both non-excludable (people cannot be prevented from using it) and non-rivalrous (one person's use does not reduce availability to others).
2. Analyze each option to see if it meets the criteria of a public good:
3. For 'A slice of pizza': it is excludable (you can prevent others from eating it) and rivalrous (once eaten, it cannot be consumed by others), so it is not a public good.
4. For 'A private swimming pool': it is excludable (only certain people can use it) and rivalrous (limited capacity), so it is not a public good.
5. For 'A toll road': it is excludable (only those who pay can use it) and rivalrous to some extent (congestion can reduce availability), so it is not a pure public good.
6. For 'National defense': it is non-excludable (everyone benefits regardless of payment) and non-rivalrous (one person's protection does not reduce protection for others), so it is an example of a public good.