Sources of Nitrogen Oxides (NOx)

Steps:

• Identify natural sources: Lightning (electrical discharges) fixes atmospheric N2 and O2 into NOx.
• Identify man-made sources: High-temperature combustion in engines produces NOx from air.
• Evaluate options for one accurate natural and one man-made source.
• Select the pair matching both categories.

Why A is correct:

• Electrical discharges naturally form NOx via N2 + O2 → 2NO at high temperatures; internal combustion engines produce NOx similarly during fuel burning.

Why the others are wrong:

• B: Haber process synthesizes NH3 from N2 and H2, not NOx.
• C: Decomposition of dead plants in rivers produces N2 via denitrification, not NOx.
• D: Links incorrect natural source (decomposition yields N2) to incorrect man-made (Haber process for NH3).

Final answer: A