Which of the Following Describes a Positive Externality

Multiple Choice

Which of the following describes a positive externality?

A) John Henry paints the outside of his house in order to increase its market value just before he puts the house up for sale.
B) People who do not attend college still benefit from others who receive a college education.
C) The government imposes a tax on cigarettes in order to discourage smoking among teenagers.
D) Mary volunteers to drive her neighbor's children to soccer practice.