The altitude at which air reaches saturation cloud formation begins is the.

Explanation:

A cloud is formed when so much water vapor or gas is contained in a air. This is called the saturation point. This point can be achieved in two ways.

First, moisture gathers until it reaches the maximum amount the volume that air can hold.

Second,  the reduction of the temperature of the moisture filled air, which lowers the amount of moisture it can contain. Saturation can therefore be reached through evaporation and condensation, respectively. When saturation occurs, moisture will become water droplets that are visible in the form of fogs and clouds.

The point at which water vapour condenses is the point when air reaches saturation.

In terms of altitude, there is a clear distinction between fogs and clouds. This is because the fogs are visible moisture that begins to form at a height lower than 50 feet. While clouds are visible moisture that begins to form at or above 50 feet.