Why was 1990 an important year regarding air quality? O The United States took first steps to keep the air clean.
O The United States created the Environmental Protection Agency.
Modifications and improvements were made to the Clean Air Act.
O Funding was established under the Clean Air Act to study air pollution.

C. Modifications and improvements were made to the Clean Air Act.

Explanation:

The Clean Air act was originally established in 1970 and was concerned with the aim of protecting people and the environment in general from polluted air. Polluted air could cause different illnesses and environmental degradation.

The law was amended in 1990 in which modifications and improvements were made to the Clean Air Act. There was the need to reduce acid rain, toxic emissions which could deplete the ozone layer and cause varying respiratory illnesses in humans and to increase visibility.

yes

explanation:

search chemistry final b exam in google and a site called quizlet will pop up

it should be all of them because it asks if you included all of those in your answer

explanation: