Diffusion can be defined as active transport of particles up a concentration gradient.

movement through a cell membrane using energy from ATP

movement of particles from a region of high concentration to a reaigon of low conentration

movement of particles from a region of low concentration to a regoin or to a high region

Movement of particles from a region of a high concentration to a region of low concentration

Option (3).

Explanation:

The molecules may transport from inside and outside of the cell from their region of low concentration to high concentration or vice-versa. Different types of transport process are diffusion, osmosis, primary active transport.

Diffusion occurs naturally in the organism and no energy is required for its transport. The molecules move to the region of lower concentration from its region of higher concentration. The molecules moves along the concentration gradient.

Thus, the correct answer is option (3).