If surface temperature is below freezing and water vapour changes directly into ice crystals, this is an example of what?

Correct answer: Frost formation

Correct answer: B, frost formation. The key clues are “below freezing” and “directly into ice crystals.” In this situation, water vapour does not first become liquid water; it changes directly into solid ice on a cold surface. This phase change is called deposition, and the ice crystals formed on exposed surfaces are called frost. B is correct because frost is the freezing or deposition-related surface form of condensation under sufficiently cold conditions. A is wrong because dew consists of liquid water droplets and is normally associated with surface temperatures above freezing. C is wrong because an ocean tide is the periodic rise and fall of sea level caused mainly by gravitational effects, not a phase change of water vapour. D is wrong because evapotranspiration is the transfer of water to the atmosphere through evaporation and plant transpiration, not the formation of ice. Memory cue: dew is liquid on a surface; frost is ice crystals on a surface. The word “directly” points to deposition.