If the red blood cells (RBCs) of human blood are isolated and are dilu

If the red blood cells (RBCs) of human blood are isolated and are diluted in normal saline (an isotonic solution to blood), what will happen to the RBCs?

The RBCs will swell
The RBCs will swell and burst
The RBCs will shrink
No change in the diameters of the RBCs
This question was previously asked in
UPSC CDS-1 – 2023
If red blood cells are placed in normal saline, there will be no change in their diameters.
Normal saline (0.9% sodium chloride solution) is isotonic to the cytoplasm of human red blood cells. This means it has the same solute concentration and thus the same water potential as the inside of the RBCs.
In an isotonic solution, there is no net movement of water across the cell membrane via osmosis. Water molecules move in and out of the cell at equal rates, maintaining the cell’s shape and volume. If RBCs were placed in a hypotonic solution (lower solute concentration), water would enter the cells causing them to swell and possibly burst (hemolysis). If placed in a hypertonic solution (higher solute concentration), water would leave the cells causing them to shrink (crenation).