Why may dew be seen on grass in the morning but less on a nearby warmer road?

Correct answer: Grass can provide a cooler surface at night

The correct answer is B: grass can provide a cooler surface at night. Dew forms when a surface cools to or below the dew point of the nearby air. After sunset, grass blades can lose heat by radiation and may cool efficiently. If their temperature reaches the dew point, water vapour in contact with them condenses into tiny liquid droplets. A road may remain warmer because it stores heat absorbed during the day, so its surface may not reach the dew point and less dew forms there. A is wrong because water vapour is present in the air above both surfaces. C is wrong because dew is surface condensation, not cloud formation. D is physically unrelated: grass does not make air pressure zero. The exact amount of dew also depends on wind, sky condition, humidity, and surface properties. Memory cue: dew needs a cool surface plus moist air, not merely a cool morning.