Public Goods: Non-Excludable and Non-Rivalrous

Steps:

• Define a public good as something non-excludable (no one can be prevented from using it) and non-rivalrous (one person's use doesn't reduce availability for others).
• Evaluate each option against these criteria.
• Identify which option fits both properties perfectly.
• Confirm by excluding options that fail one or both tests.

Why A is correct:

• Flood defences are non-excludable (everyone in the area benefits regardless of payment) and non-rivalrous (protection for one doesn't diminish it for others), per the standard economic definition.

Why the others are wrong:

• B: Government-funded hospitals are excludable (access can be restricted to patients or payers).
• C: Government-run national parks are rivalrous (overcrowding limits enjoyment) and often excludable (via entry fees).
• D: The internet is excludable (requires subscriptions) and rivalrous (bandwidth congestion affects users).

Final answer: A