Final answer:
Crenation occurs when blood cells are placed in a hypertonic solution, causing them to lose water and shrink due to the higher external solute concentration.
Step-by-step explanation:
Crenation is likely to occur in blood cells in a hypertonic solution. A hypertonic solution has a higher solute concentration than the cytoplasm of red blood cells, leading to water moving out of the cell into the external environment to balance the solute concentrations. Consequently, red blood cells lose water and shrink, causing the crenation effect. In contrast, cells maintain their normal shape in an isotonic solution because the flux of water into and out of the cell is balanced. Exposure to a hypotonic solution results in cells swelling as water moves into the cell to balance the lower external solute concentration, potentially leading to hemolysis.