When a bacterial cell is placed in a solution containing NaCl (such as 5% NaCl), the solution is hypertonic relative to the bacterial cytoplasm. This causes water to move out of the bacterial cell by osmosis, leading to plasmolysis where the cell membrane shrinks away from the cell wall due to water loss. Thus, the best description is that water moves out of the bacterial cell

. This osmotic effect is because NaCl dissociates into sodium and chloride ions, which bind water molecules and reduce water activity outside the cell, drawing water out of the cell to balance solute concentrations

. The loss of water can inhibit bacterial growth and affect cellular functions, including biofilm formation and motility

. In summary, the key event when a bacterial cell is placed in a NaCl solution is:

• Water moves out of the bacterial cell due to the hypertonic environment created by NaCl, causing plasmolysis and potential inhibition of growth and function