Why do not all cloud droplets fall out of the sky?

The correct answer highlights the balance between gravitational pull and the upward force exerted by wind drag on cloud droplets. When cloud droplets form, they are very small, often on the order of a few micrometers in diameter. Their mass is light enough that, although gravity pulls them downward, the drag force created by the surrounding air can counteract this gravitational force.

As droplets begin to fall, the resistance from the air (wind drag) increases with their velocity. For very small droplets, the drag force can equal and even exceed the force of gravity due to this balance, allowing them to remain suspended in the cloud rather than falling to the ground. This phenomenon is more pronounced in clouds where updrafts and turbulent wind conditions exist, keeping many droplets aloft, despite the gravitational force acting on them.

Other options do not capture the complexity of this balance. While wind drag is mentioned, the nuances of cloud density and how temperature variations affect droplet behavior do not directly address why not all droplets fall out of the sky. Understanding this balance is essential for comprehending phenomena like cloud formation, precipitation processes, and weather systems.