Answer: The correct answer is A) Cells swell as water moves into them.
Due to drinking of water during exercise, the concentration of sodium ( solute) in the blood becomes lower than the normal. The concentration of solvent ( water) will be high outside the cells.
When the body tries to restore homeostasis, the cells swell as the water moves from outside the cell to inside. This is because water always moves from an area of its high concentration to the area of its low concentration. As the solute concentration is low and solvent ( water) concentration is high outside the cell. Therefore, water moves in the cells making them swell.
Thus, the correct option is A) Cells swell as water moves into them.