All questions carry equal weight.
Answers should be 1 to 3 complete sentences and should fit in the space provided. Name two natural sources and two natural sinks of atmospheric carbon dioxide. Name two anthropogenic sources of methane. Name two atmospheric pollutants that originate from the burning of fossil fuels, and describe their effects on human health. On one particular hypothetical day, the air in Tucson and Phoenix contains 5 grams of water vapor per kilogram of air.