What kind of air is useful for mist formation?

Correct answer: Moist and cool

Direct answer: A, moist and cool air. Mist forms when air contains enough water vapour and cools sufficiently for condensation into tiny droplets. Cooling toward the dew point is important, while moisture supplies the water that becomes visible. A is correct because it provides both necessary conditions: available moisture and cooling. B is wrong because warm, dry air is usually far from condensation and lacks sufficient moisture. C is wrong because cooling alone is not enough if the air is extremely dry; there may be too little water vapour to form many droplets. D is wrong because air without water vapour cannot produce mist at all. Wind and local conditions also influence formation and persistence, but the basic requirement remains moist air that cools to saturation or near saturation. Memory cue: mist needs “moisture plus cooling.” Do not confuse cool air with dry air; cool, moist air is the favourable combination.