The force driving simple diffusion is the concentration gradient, while the energy source for active transport is ATP (Adenosine Triphosphate).

Explanation:
The force driving simple diffusion is the concentration gradient, which is the difference in the concentration of a substance between two regions.

Substances move from an area of high concentration to an area of low concentration, which is a passive process and does not require energy input.

In contrast, the energy source for active transport is adenosine triphosphate (ATP), which is a molecule that cells use to store and transfer energy.

Active transport is the movement of molecules or ions against their concentration gradient, from an area of low concentration to an area of high concentration. This process requires energy input to move the molecules or ions across the cell membrane, often with the help of specialized transport proteins.