Identifying the four major air pollutants

Steps:

• Recognize the four key pollutants as sulfur dioxide (SO2), carbon dioxide (CO2), methane (CH4), and nitrogen oxides (NOx), based on common environmental science classifications for emissions impacting air quality and climate.
• Examine each choice for the exact sequence matching standard listings in pollution control frameworks.
• Note that official orders often prioritize SO2 for acid rain, followed by CO2 and CH4 as greenhouse gases, then NOx for smog.
• Select the option aligning with this sequence: SO2, CO2, CH4, NOx.

Why B is correct:

• B matches the conventional order in Clean Air Act-related regulations and IPCC reports, starting with SO2 as a criteria pollutant, then CO2 and CH4 for radiative forcing, and NOx for tropospheric ozone formation.

Why the others are wrong:

• A starts with CO2, disrupting the priority for criteria pollutants like SO2.
• C begins with CH4, which is secondary to industrial SO2 emissions.
• D swaps CH4 and NOx, inverting their relative impacts on acid rain versus greenhouse effects.

Final answer: B