Answer:
a. a command-and-control approach to pollution reduction.
Explanation:
Command-and control policies are used by the federal government when it orders companies to use particular methods to reduce pollution.
The rest of the options are incorrect because tradable allowances are government permissions for private companies to do something that can be environmentally damaging; the Pigovian method is a taxation imposed to firms whose products or services cause negative externalities, such as pollution or health issues; finally, the Coasian system involves a compensation between different parties in pollution cases.
