On which surfaces is frost generally more clearly visible?

Correct answer: On cold grass, leaves and open ground

Direct answer: A, on cold grass, leaves, and open ground. Frost is a deposit of ice crystals or a thin icy coating that develops when a surface becomes sufficiently cold and nearby moisture freezes or changes into ice crystals. Open surfaces such as grass, leaves, and exposed ground can lose heat during clear, calm nights, so frost may be clearly seen on them as a whitish layer. A is correct because it identifies common cold, exposed surfaces. B is wrong because hot iron and fire keep surfaces too warm for frost to remain. C is not the usual visible setting meant by this question; submerged rocks are surrounded by water and are not typical frost surfaces. D is wrong because frost is not restricted to areas above clouds and is commonly observed near the ground. The exact occurrence depends on temperature, moisture, wind, and exposure. Memory cue: frost is white ice on a cold exposed surface.