In winter, water vapours and pollutants comes to lie in the lowermost layer of atmosphere by -

Ans. is `c' i.e., Temperature inversion A temperature inversion is a thin layer of the atmosphere where the normal decrease in temperature with height swithees to the temperature increasing with height. An inversion can lead to pollution such as smog being trapped close to the grand (lower layers of atmosphere). Temperature inversion may occur during the passage of a cold front or result from the invasion of sea air by a cooler onshore breeze. o Overnight radiative cooling of surface air often results in a nocturnal temperature inversion that is dissipated after sunrise by the warming of air near the ground.