Proteins contain nitrogen, leading to NOx formation in combustion

Steps:

• Examine chemical composition: fats are lipids (C, H, O), proteins include amino acids (C, H, O, N), starch is a carbohydrate (C, H, O), Terylene is a polyester (C, H, O).
• Identify nitrogen presence: only proteins have nitrogen atoms.
• Consider combustion process: burning organic compounds oxidizes elements; nitrogen in proteins forms NO or NO2.
• Match to question: substance producing nitrogen oxides must contain nitrogen.

Why B is correct:

• Proteins contain nitrogen in amino groups; combustion follows the reaction where N combines with O2 to form NOx, as in 4NH3 + 5O2 → 4NO + 6H2O (simplified for organic N).

Why the others are wrong:

• A. Fat: Composed of C, H, O only; combustion yields CO2 and H2O, no nitrogen for NOx.
• C. Starch: Pure carbohydrate (C6H10O5)n; burns to CO2 and H2O, lacking nitrogen.
• D. Terylene: Synthetic polymer from ethylene glycol and terephthalic acid (C, H, O); combustion produces CO2, H2O, no NOx.

Final answer: B