Atmospheric Gases and Their Roles Steps: - Evaluate each statement against established environmental science facts. - Confirm A: Catalytic converters oxidize CO to CO2, which is accurate but focuses on emission control rather than direct atmospheric composition. - Confirm B: Methane contributes to tropospheric ozone formation, not depletion of the stratospheric ozone layer. - Confirm C: Photosynthesis by plants and algae releases O2 as a byproduct, maintaining atmospheric oxygen levels. - Confirm D: CO is a toxic pollutant but does not form acids; acid rain results from SO2 and NOx. Why C is correct: - Photosynthesis follows the equation 6CO2 + 6H2O → C6H12O6 + 6O2, directly adding oxygen to the atmosphere. Why the others are wrong: - A: The statement is technically true for emission reduction, but the question seeks core atmospheric processes, not technology. - B: Methane oxidation produces tropospheric ozone and is a greenhouse gas, but ozone-depleting substances are mainly CFCs and halons. - D: Acid rain forms from sulfurous and nitric acids (SO2 + H2O → H2SO3; NO2 + H2O → HNO3); CO is an asphyxiant …