Answer:
C. isotonic
What is a isotonic solution?
Two solutions exerting the same osmotic pressure over a semipermeable barrier are said to be in an isotonic solution. Without affecting the concentration of solutes on either side, this condition enables unrestricted passage of water over the membrane.
What is osmosis?
The tendency of a fluid, usually water, to pass through a semipermeable membrane into a solution where the solvent concentration is higher, thus equalizing the concentrations of materials on either side of the membrane.