In which example is condensation clearly visible?

Correct answer: Droplets forming outside a cold glass

Direct answer: C. Condensation is the change of water vapour from a gas into liquid water. Air near a cold glass is cooled by the glass. If that air reaches its dew point, the water vapour can no longer remain entirely as an invisible gas, so it forms liquid droplets on the outside surface. The water on the glass does not normally pass through the glass; it comes from water vapour in the surrounding air. A describes movement of dust by wind, not a change of water vapour. B results from drying and shrinkage of soil, so it is not condensation. D describes heating and may encourage evaporation, which is the opposite change. The visible droplets make this a clear everyday example. Memory cue: cold surface plus moist air often produces condensation.