The model shows a substance crossing a cell membrane.

Three illustrations shown side by side. All three illustrations show a cell membrane, the inside of a cell, and the outside of a cell. In the first illustration there are more solute particles outside of the cell than inside of the cell. In the second illustration there are still more particles outside the cell than inside the cell, but there are now less particles outside the cell than in the first illustration and more particles inside the cell than in the first illustration. There are four arrows. Three arrows are pointed toward the inside of the cell. One arrow is pointed toward the outside of the cell. In the third illustration there is the same number of particles on the outside of the cell as inside the cell. There are four arrows. Two arrows are pointed toward the inside of the cell. Two arrows are pointed toward the outside of the cell.

Which of the following describes the process?
A. The model shows the process of active transport because the solute particles are moving from an area of low concentration to an area of high concentration.
B. The model shows the process of bulk transport because the solute particles are moving from an area of low concentration to an area of high concentration.
C. The model shows the process of diffusion because solute particles are moving from an area of high concentration to an area of low concentration.
D. The model shows the process of osmosis because the solute particles are moving from an area of high concentration to an area of low concentration.