Concept:Isotonic solutions have equal solute concentrations on both sides of a cell membrane.
Explanation:When the solute concentration inside a cell is the same as that of the surrounding medium, there is no net movement of water.
Water moves across a membrane from a region of higher water concentration to a region of lower water concentration.
Because the concentrations are equal, water moves in and out at the same rate.
This balanced condition is called an isotonic solution.
It means the cell neither gains nor loses water.
The cell maintains its normal shape and size.
In contrast, a hypertonic solution has a higher solute concentration outside the cell, causing water to leave the cell.
A hypotonic solution has a lower solute concentration outside the cell, causing water to enter the cell.
Since the two concentrations are identical, the solution is isotonic.
Answer:C. isotonic