Answer: d. Its base at or near the ground.
Step-by-step 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.