Question

what is the most effective approach the government can take to keep the air clean?
create and enforce regulations that limit fossil fuel burning by industries
use funds to understand why smoke and mold are causes of outdoor air pollutants
educate people about the threats to outdoor clean air from visible forms of air pollution
modify regulations under the clean air act by including expensive options to reduce air pollution

Explanation:

• Creating and enforcing regulations that limit fossil fuel burning by industries directly targets a major source of air pollution. Industries are significant emitters, and such regulations can have a broad - scale impact.
• Using funds to understand why smoke and mold are causes of outdoor air pollutants is more of a research - oriented step rather than a direct action to keep the air clean.
• Educating people about visible forms of air pollution is important but may not be as effective as regulatory action against a major source (industries).
• Modifying regulations under the Clean Air Act by including expensive options may not be the most practical or effective approach as it could face resistance due to cost.

Answer:

create and enforce regulations that limit fossil fuel burning by industries