A) a gas; visible
B) a gas or liquid; manmade
C) toxic; gas
D) a gas, liquid, or solid; harmful
E) biogenic; visible

A) Asbestos is not an air pollutant.
B) Sulfur dioxide can come from natural sources.
C) Forest fires are a source of air pollution.
D) Air pollution can cause cancer.
E) Respiratory diseases can originate from air pollution.

A) 10
B) 25
C) 50
D) 75
E) 90