Explanation:

• Stratus is used to describe flat, featureless clouds of low altitude, typically less than 300 metres. On the other hand, fog is a stratus cloud in contact with the ground. Horizontal visibility in fog is less than 1 km.
• The only real difference between Fog and Stratus is the different altitude of the cloud base, which for Stratus lies a few hundred meters above ground, whereas in Fog the cloud base descends to ground level.