What is the main difference between frost and snowfall?

Correct answer: Frost forms by deposition on surfaces, snowfall falls from clouds

The correct answer is A. Frost is a surface deposit of ice. It forms when a surface becomes sufficiently cold, usually at or below the freezing point, and water vapour deposits directly as ice or freezes on that surface. Snowfall is precipitation produced in clouds; ice crystals or snowflakes grow in the cloud and then fall through the atmosphere to the ground. Thus, the key difference is the place and process of formation: frost forms on a surface, whereas snow forms in clouds and falls. B is wrong because frost does not always fall with rain. C is wrong because snowfall can cover many surfaces, not only grass. D is wrong because the two processes have different origins. Memory cue: “frost forms on the ground; snow falls from the sky.”