What is diffusion?

Answer

The correct answer is: 'The movement of the molecules through a semi-permeable membrane from an area of a higher concentration to an area of lower concentration'. Diffusion is a passive process resulting from the random motion of molecules. This motion leads to the net movement of particles from a region where they are more densely packed (high concentration) to a region where they are less densely packed (low concentration) until equilibrium is reached. It does not require energy input from the cell, as molecules naturally move down their concentration gradient.