Answer:
The correct answer is option D.
Explanation:
An externality can be defined as a situation in which the benefit or cost resulting from an activity is received or incurred by a third person.
A positive externality means a third person receives the benefits of someone else's activities.
If the marginal social benefit earned from the consumption of a good is higher than the marginal private cost incurred then in that case we can say that a positive externality exists in the market.
People have to pay less but are having greater profit.
