Final answer:
The correct definition for a public good is option 'D', as it addresses the nonexcludable and non-rival features of public goods, meaning they can't be provided to one person without it being available to others and one's use does not prevent use by another.
Step-by-step explanation:
The student asked which statement correctly defines a public good. A public good has two key characteristics: it is nonexcludable and non-rival. The correct option, in this case, is 'D. Cannot be provided to one person without making it available to others as well,' which highlights the nonexcludable nature of public goods meaning it is difficult to prevent others from using it once provided and their non-rival nature meaning one person's use of the good doesn't diminish the availability to others. Public goods often experience the free rider problem, where individuals benefit without paying, and thus the market alone struggles to provide such goods without mechanisms for ensuring payment, such as government intervention.