Final answer:
A public good is D) Can't be provided to one person without making it available to others as well, characterized by its nonexcludable and non-rival nature.
Step-by-step explanation:
The correct answer to the student’s query about a public good is D) Can't be provided to one person without making it available to others as well. Public goods are defined by their nonexcludable and non-rival nature.
Being nonexcludable means it's difficult to prevent others from using the good, and non-rival implies that one person's use doesn't diminish the availability for others.
While it's a common misconception that public goods result in negative externalities or cost nothing to produce, they in fact may involve substantial production costs and often do not cause negative externalities.
Furthermore, both governments and nongovernmental organizations can provide public goods, as seen in the case of the radio, which broadcasts signals that are nonexcludable and non-rival but can be provided by private companies through advertising revenue.
Non-rival means that when one person uses the good, it does not prevent others from using it. Examples of public goods include roads, parks, dams, and libraries. These goods are typically provided by the government and funded through taxes. Private companies find it difficult to produce public goods because it is challenging for them to charge people for goods that are nonexcludable.