Why does glass become misty when moist air touches a cold surface?

Correct answer: Because water vapour in air condenses into tiny droplets on the cold surface

Direct answer: A is correct. Moist air contains water vapour that is invisible as a gas. When this air touches a cold glass surface, the air immediately next to the glass is cooled. Cooling lowers its saturation capacity. If that local air reaches its dew point, it becomes saturated and some water vapour changes into liquid water. The liquid appears as a very large number of tiny droplets spread over the glass; these droplets scatter light, so the glass looks misty or cloudy. A is correct because it describes condensation on a cold surface. B is wrong because vapour does not turn into dust. C is wrong because air remains present near the glass. D is wrong because the appearance is caused by droplets and light scattering, not by the Sun hiding inside the glass. The droplets may later evaporate when the glass warms or the surrounding air becomes drier. Memory cue: cool surface, dew point, tiny droplets, misty glass.