When red blood cells are placed in a 1% salt solution, they will shrink. This phenomenon is known as crenation.
The explanation lies in the principles of osmosis and the differences in solute concentration. Red blood cells typically have a solute concentration of around 0.9%, which is isotonic to blood plasma. When they are placed in a solution with a higher solute concentration (1% salt solution), water begins to move out of the cells in an attempt to balance the solute concentration inside and outside the cells.
This outward movement of water leads to a decrease in the volume of the cells, causing them to shrink. If the external solution were hypotonic instead (having a lower concentration than the cell’s interior), water would flow into the cells, potentially causing them to expand and even burst. However, in this case, since the surrounding salt concentration is higher, therefore, option b) the cells will shrink is the correct answer.