Which of the Following Is NOT an Example of a Corrective

Which of the following is NOT an example of a corrective tax or subsidy used to address an externality problem?

A) The government charges Ku's company a tax equal to the difference between the marginal social cost and the marginal private cost of emissions.
B) The government discourages the production of paper products in a suburban community by imposing a unit tax on the production of such products, limiting paper companies' emissions of carcinogenic toxins.
C) Marlo's customers have been bothered by the noisy, midday deliveries at the business next door. She arranges to cover part of the delivery costs in order to have the neighbor's deliveries arrive early in the morning rather than at midday.
D) The government covers part of the cost of a particular immunization.