Why can fog be called a cloud near the ground?

Correct answer: Because it is made of tiny water droplets in air

Direct answer: C, because fog is made of tiny water droplets suspended in air near the ground. A cloud is a visible collection of tiny water droplets, ice crystals, or both in the atmosphere. Fog has essentially the same physical nature, but its base is at or very close to the Earth’s surface. This is why it is often described as a cloud at ground level. C is correct because it identifies the suspended droplets that make fog visible. A is wrong because dust alone does not constitute fog, although particles may sometimes help condensation. B is wrong because fog is not restricted to the sea; it can occur over land, valleys, roads, and other areas when conditions are suitable. D is wrong because fog forms in the atmosphere, not inside the Earth. The main difference between an ordinary cloud and fog is height above the surface, not the basic presence of tiny droplets. Memory cue: a cloud above, fog below; both are made of minute atmospheric droplets.