For cells to stay the same size from generation to generation, what two things must be coordinated?

The correct answer is growth and division.

The cell growth is the term that is used in the perspectives of cell division (reproduction) and biological development of the cell. When used in the perspective of cell division, it is considered as proliferation, where a cell called as the mother cell divides and grows to generate the daughter cells.

While in the perspective of cell development, the term signifies towards the enhancement in the cytoplasmic and organelle volume, as well as the increase in the genetic material succeeding the replication at the time of S-phase.