One of the key changes made in the 1990 clean air act amendment was the emphasis made of finding cost-effective ways to reduce air pollution call for the total elimination of emissions by 2000 inclusion of the regulations against deforestation addition of funding to pay for health care of individuals affected by air pollution

One of the key changes made in the 1990 Clean Air Act amendment was the EMPHASIS MADE OF FINDING COST-EFFECTIVE WAYS TO REDUCE AIR POLLUTION.

The Clean Air Act is a federal law designed to control air pollution nationwide. The Environmental Protection Agency (EPA) is required to develop and enforce the regulations to protect the general public from exposure to air pollutants that are known to be dangerous to human health. The 1963 law established a basic research program, which was expanded in 1967. The main changes to the law, which require regulatory controls of air pollution, were promulgated in 1970, 1977 and 1990.

In the 1990 amendment, provisions were added to deal with acid rain, depletion of the ozone layer and toxic air pollution; a program of national permissions of fixed sources was established. Also new requirements were established for the reformulation of gasoline, the adjustment of Reid Vapor Pressure (RVP), which measures the volatility of gasoline; and the norms to control the evaporation emissions of the gasoline.

the answer is option a.