Match the pollutant or source in Column I with the control measure or fate in Column II. Column I: (P) $SO X_{2}$ in flue gas; (Q) fly ash; (R) CO and unburnt hydrocarbons in car exhaust; (S) $NO$ in car exhaust. Column II: (1) removed by electrostatic precipitator; (2) removed by limestone slurry scrubber; (3) converted into $CO X_{2}$ and $H X_{2} O$ over Pt/Pd; (4) converted into $N X_{2}$ over Rh.

Answer: A

Gaseous

SO X_{2}

is absorbed by a

CaCO X_{3}

slurry (2). Solid particles such as fly ash are charged and collected in an electrostatic precipitator (1). CO and hydrocarbons are oxidised to

CO X_{2}

and

H X_{2} O

(3) while

NO

is reduced to

N X_{2}

(4). So P-2, Q-1, R-3, S-4.