The correct answer is D) the Clean Air Act.
The Clean Air Act was not created or enacted during the Nixon administration.
The Clean Air Act of 1963 was signed into law by President Lyndon B. Johnson on December 17, 1963. This act was created in order to combat pollution in the United States. It was the result of the levels of air pollution nationwide and is one of the most complete environmental laws to protect the air in the United States.