Answer:
The concentration gradient is the driving force.
Explanation:
Passive transport of substance occurs when they are moved from the region of their higher concentration to that of their lower concentration. The concentration gradient is the difference in the concentration of substances between two regions or across the membrane. The concentration gradient of substances drives their passive movement. The passive movement of substances does not use metabolic energy. Simple diffusion and facilitated diffusion are two examples of this transport.
Um I thought it was salt and water? I might be wrong though..
