The correct option is B p - (ii), q - (iii), r - (i)
A catalytic converter is an emission control device that converts toxic gases and pollutants in exhaust gas to less toxic pollutants by catalysing a redox reaction. They have metals like platinum, palladium and rhodium as catalysts and are fitted into automobiles to reduce emission of poisonous gases.
An electrostatic precipitator can remove close to 99% of particulate matter. It has electrodes that are maintained at several thousand volts, which produce a corona that releases electrons. These electrons attach to dust particles from the exhaust, giving them a net negative charge. The charged dust particles settle down as they are attracted to the collecting plates.
Scrubbers work on a single target pollutant and have water or designed adsorbent fluids, which are sprayed down through a rising column of flue gas. This motion of particles facilitates reactions and the pollutant gas dissolves in the wash, which is then purified or discarded.