In which situation is a cell most likely to swell and potentially burst?

When a cell is placed in a hypotonic solution, it is surrounded by a solution that has a lower concentration of solutes compared to the inside of the cell. This difference in solute concentration creates an osmotic gradient, causing water to move into the cell through osmosis in an attempt to equalize the solute concentrations on both sides of the cell membrane. As water enters the cell, it causes the cell to swell. If enough water continues to enter, the pressure from the internal increase of water can lead to the cell eventually bursting, a process known as lysis.

In contrast, when a cell is in a hypertonic solution, water would move out of the cell, leading to cell shrinkage. In an isotonic solution, there would be no net movement of water, so the cell would maintain its shape and volume. A buffered solution maintains a stable pH, but it does not inherently impact the osmotic balance that would lead to swelling or bursting of the cell. Thus, a hypotonic solution is the one that presents the highest risk for the cell to swell and potentially burst.