If moist air reaches cold grass and the grass temperature falls to the dew point above 0°C, what will form?

Correct answer: Dew

Correct answer: A, dew. First identify the surface process: moist air is in contact with cold grass, and the grass cools to the dew point. At the dew point, the air next to the surface becomes saturated, so excess water vapour changes into liquid water droplets on the grass. The condition that the temperature is above 0°C is decisive: the condensed water remains liquid, so it is called dew. A is correct because dew is surface condensation in liquid form. B is wrong because frost consists of ice crystals and requires freezing conditions, usually a surface temperature at or below 0°C, with deposition or freezing involved. C is wrong because hail is a form of solid precipitation produced in strong thunderstorm clouds, not surface condensation on grass. D is unrelated to water-vapour condensation. Memory cue: above freezing gives dew; below freezing gives frost, provided the relevant moisture and cooling conditions exist. The dew point is the threshold at which condensation begins, not a separate type of precipitation.