A key feature of a public good is:

A) overproduction in the private market.
B) rival consumption.
C) payment through charitable contributions.
D) nonexclusion.

A key feature of a public good is nonexclusion, meaning that it is not possible to prevent individuals or groups from benefiting from the good or service, even if they do not contribute to the cost of producing it. Public goods are typically not produced in sufficient quantities by the private market due to the lack of financial incentives, which leads to market failure. Rival consumption, on the other hand, refers to the fact that the consumption of private goods reduces the amount available for others to consume, while public goods can be consumed by an unlimited number of individuals without diminishing the resource for others. Payment through charitable contributions may occur, but it is not a defining characteristic of public goods.