The Clean Air Act of 1972 required some companies to install the "best available" pollution control technologies

The Clean Air Act of 1972 required some companies to install the "best available" pollution control technologies; this is an example of C. the government using the command approach to discourage a negative externality.

Under command approach, the government addresses the problem of a negative externality by either calling for or prohibiting particular actions. The government will forbid an action if the external cost of the action to the society surpasses the gain to the polluter. If it is not possible to forbid the entire production activity, however, the government can require the company to adopt a specific technology to decrease pollution. Before coming up with such a regulation, it is good for the government to comprehend the details concerning the industry in question and the substitute technologies the firms can access.