Since transport of materials in and out of the cell can only happen at the cell's surface, what happens as cells get larger? How does this impose a limit on cell size?

The surface area/volume ratio will decrease

Explanation:

How does this impose a limit on cell size?

Because the ability of a cell to exchange substances with its environment is proportional to its surface area.

Hence, if surface area/volume decrease and get too small, surface area is not sufficient to take up substances needed to support metabolism or get rid of wastes.

the answer is c) an oak tree