根据材料回答下列各题: It can be inferred from the first paragraph that______.A.water
根据材料回答下列各题:It can be inferred from the first paragraph that______.
A.water vapor is an air pollutant in localized areas
B.the definition of air pollutiom will continue to change
C.a substance becomes an air pollutant only in cities
D.most air pollutants today can be seen or smelled