Answer:
The correct answer is d. increases at a slower rate.
Explanation:
As the volume of a cell increases a cell grows bigger but unfortunately the surface area does do not increase as faster as the volume, therefore, the relative surface area amount which is available to pass the molecule across plasma membrane per unit volume decreases.
Therefore as the cell increase in size the surface area to volume ratio decreases. So if a cell grows more than its limit it will get difficult to move molecule fastly across its membrane. Therefore the correct answer is d.