What is the approximate date for the earth's formation?
a. 4 billion bc
b. 4.5 billion bc
c. 4,000 bc
d. 1 trillion bc
e. it was there forever

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