Instructions: Choose One Answer from Each Pair of Selections

Q20: Photochemical smog _.<br>A) only forms at night<br>B)

Q21: Which substance is considered a primary pollutant?<br>A)

Q22: Which gas is a major source of

Q23: Instructions: Choose one answer from each pair

Q24: Which pollutant is formed during the incomplete

Q26: In which area would air pollution typically

Q27: Explain how the semipermanent Pacific high off

Q28: Where was the term smog first used,

Q29: Since the 1970s, the overall trend in

Q30: Ozone in the stratosphere primarily forms over