In living things, cells must be in a solution where water leaves and enters the cell at .

isotonic; the same rate

Explanation:

Cell Theory as as commonly known gives the best definition for cells. All organisms that ever existed are made up of one or more cells. The theory state that the cell is a basic unit, that is of all living things, and that all cells come from cells that have existed.

For cell that is in an isotonic solution,no net flow of water into or out of the cell will be experienced, the volume of the cell is at a state of stability. When the level or concentration of solute in and out of the cell is at the same pace or level, the the cell membrane does not allow solutes to cross, leading to the solution being isotonic to the cell.