A Uniform Per-Unit Tax on Pollution Achieves Abatement in the Least

A uniform per-unit tax on pollution achieves abatement in the least costly manner because:

A) the government is completely informed about the marginal costs of installing environment friendly equipment to the firms.
B) the government subsidizes the equipment required for pollution control.
C) each firm will ensure that reduce pollution to zero.
D) each firm reduces pollution until the marginal cost of abatement equals the per-unit tax.