Answer:
A solution should be isotonic in order to prevent water gain or water loss in a cell.
Explanation:
An isotonic solution can be described as a solution that has equal amounts of solutes outside the cell as well as inside the cells. In such a kind of solution, no transfer of water or solutes will take place. Hence, there will be no loss or gain of water in such a solution.
Any imbalance in the concentration of the solutes will cause the solution to no longer remain isotonic.