Which term refers to the diffusion of molecules?
- Amovement from a region of their higher concentration to a region of their lower concentration down a concentration gradient
- Bmovement from a region of their higher concentration to a region of their lower concentration up a concentration gradient
- Cmovement from a region of their lower concentration to a region of their higher concentration down a concentration gradient
- Dmovement from a region of their lower concentration to a region of their higher concentration up a concentration gradient