Answer:
Smaller as the cell gets larger [Decrease]
Step-by-step explanation:
The important point is that the surface area to the volume ratio gets smaller as the cell gets larger. Therefore, if the cell grows beyond a certain limit, not enough material will be able to cross the membrane fast enough to accommodate the increased cellular volume.
Assuming that the shape of the cell stays the same, if the cell increases it's linear dimension (length) by a factor of 2, the surface area will be increased by a factor of 4, and the volume will be increased by a factor of 8. You can verify that this is true with simple shapes such as spheres or cuboids.
The volume grows more rapidly than the surface area. Hence the surface area to volume ratio decreases.