Consider the following methods of pollution reduction;

a. the government sets a target for maximum emissions
b. the government mandates the installation of specific pollution abatement equipment
c. the government imposes a per unit tax on the good that creates pollution
d. the government gives firms a tax rebate for every unit of pollution abated

Which of the above is an example of a command -and-control approach to reducing pollution?

A. a, b, c, and d
B. a, b, and d only
C. a and b only
D. b only
E. a only