The right answer is isotonic solutions (it contains 0.9% of NaCl).
Isotony is when a solution or medium has the same osmotic pressure than another solution or medium. This is necessary to maintain the cell structure.
In biology, an isotonic solution, is a solution that has an osmotic pressure equal to that of the blood plasma. A solution that contains 9 g of sodium chloride per liter is isotonic to blood plasma.
Other conditions may be necessary such as temperature (at 37 °c) and pH neutrality.
