Fog is a cloud that has
a. a small vertical extent.
b. no ability to produce rain.
c. particles made of ice crystals.
d. its base at or near the ground

Fog is a cloud that has its base at or near the ground. The answer is letter D. Fog results when atmospheric water vapor condenses to the extent that the new forms, water droplets or ice crystals, become visible. Saturation of the air and sufficient condensation nuclei are ordinarily prerequisites for the formation of fog. One of the great hazards associated with fog is a lack of visibility.

d. Its base at or near the ground.

Explanation:

Fog is a visible weather condition in which the tiny droplets of water present in the atmosphere come together and which forms a thick cloud which lies close to the surface of the ground (land) or above the sea surface. Fog cuts the visibility down to one kilometers, it makes it difficult to observe the things through it. The fog is influenced by several factors such as wind conditions, nearby water bodies, and topography.

its first and third is your answer i did the qustion the fourth isnt right