Which of the following best explains public goods?

Public goods are defined by their characteristics of being non-excludable and non-rivalrous, which means that they can be consumed by anyone and one person's use does not diminish the availability of the good to others. This definition aligns perfectly with the answer that states goods can be consumed by anyone without diminishing availability.

For instance, consider a public park or national defense: everyone can enjoy these services without one person's enjoyment preventing another from enjoying them as well. This is why public goods often lead to challenges in allocating resources, as they are typically funded through taxation rather than direct payment.

The other choices describe features that do not apply to public goods. The first option incorrectly characterizes public goods as excludable and rivalrous, which is contrary to their fundamental nature. The third option refers to exclusive goods, which are typically private goods that not everyone can access and may be expensive. The fourth choice discusses goods available only to paying consumers, which again misrepresents public goods, as their defining characteristic is accessibility to all, regardless of payment.