The clean air act of 1990 reduces the negative externalities caused by power plant air and water pollution by
a) direct government regulationb) issuing tradable pollution permits to each power plantc) encouraging private bargaining between the power plants and the parties affected by the pollutiond) taxing power plant emissions

The correct answer is the option A: direct government regulation.

Explanation:

First of all, the Clean Air Act of 1963 is the name given to a United States federal law whose main purpose is to control the air pollution on a national level, encourage and taken care by the federal government. It is administrated by the U.S. Environmental Protection Agency or EPA by its acronomyn.

Secondly, in 1990 some major amendments were included in the original act. These amendments established an increase in the responsibility, enforcement authority and expanded research programs given directly by the federal government with the purpose of decrease the level of pollution at national level.  

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answer; empowerment and collaboration;