The difference between the two students that we know of is that they used a different meter stick. So the difference would be best attributed to the different tools they used.
Note, this is quite a huge difference. It's likely that one of the sticks, or both, are quite defect.
It would cause the cell membrane to "pop" like a balloon. b the cell would not be able to get enough of the gases and nutrients it needed. c the cell could not be part of a small organism, such as a mouse. d there would not be enough resources in the cell's environment to feed it.
The Nucleolus helps function the cell.