If the objective of economic policy is to decrease the amount of pollution by an industry in the long run, the

a. most effective policy action would be a subsidy to firms for the reduction of emissions.
b. most effective policy action would be a tax on polluting firms.
c. appropriate course of action for government is to do nothing.
d. appropriate course of action for government is to increase R&D outlays to develop technology to remove the emissions from the environment.

b