Option 1 -> Private goods are excludable and rivalrous goods owned by individuals, not non-paying users.
Option 2 -> Public goods are non-excludable and non-rivalrous goods, this describes the type of good, not the users.
Option 3 -> Free-goods is not a standard economic term for non-paying consumers.
Option 4 -> Free-riders are individuals who benefit from resources, goods, or services without paying for them.
Hence, Option 4: Free-riders -> Free-riders exploit the non-excludable nature of public goods by consuming them without contributing to their cost. This is known as the "free-rider problem" in economics, where individuals have an incentive to let others pay for public goods while they enjoy the benefits without payment. Since these goods lack exclusive property rights, it's difficult to prevent free-riders from accessing them, leading to potential under-provision of such goods in the market -> correct