Context: The diagram below shows a solution with one solute. Each solute particle is represented by a pink ball. The solution fills a closed container that is divided in half by a membrane. The membrane, represented by a dotted line, is permeable to the solute particles.
The diagram shows how the solution can change over time during the process of diffusion.
Complete the text to describe the diagram.
Solute particles moved in both directions across the permeable membrane. But more solute particles moved across the membrane (). When there was an equal concentration on both sides, the particles reached equilibrium.
A. to the right than to the left
B. to the left than to the right
Select the correct answer from the given choices and respond with the letter of the chosen option.

B