Which is an example of a public good?

A public good is characterized by two key features: it is non-excludable and non-rivalrous. This means that once the good is provided, individuals cannot be effectively excluded from using it, and one person's use of the good does not reduce its availability to others.

The army is an excellent example of a public good because its protection services are available to everyone in a nation without the ability to exclude anyone from benefiting from national defense. When the army is deployed to protect a country, all citizens benefit from its presence, regardless of whether they contributed to its funding through taxes or not. Additionally, one person’s enjoyment of security from the army does not diminish the security available to others.

In contrast, other choices like a rock band, a car, and bread do not meet the criteria for public goods. A rock band provides entertainment to a specific audience and can choose who attends a concert (excludable) while also being limited in how many people can experience the performance at once (rivalrous). A car and bread are both products that are excludable, meaning ownership can restrict who uses them, and their consumption by one person implies they cannot be consumed by another at the same time.

Thus, the army stands out as a clear