A cell is placed in a solution and it swells. This solution is _

Explanation

When a cell is placed in a hypotonic solution, the concentration of solutes outside the cell is lower than inside the cell. This causes water to move into the cell due to osmosis, leading to the cell swelling. In contrast, an isotonic solution would not cause any change in cell size as water movement is balanced, and a hypertonic solution would cause the cell to shrink as water moves out. Therefore, the correct answer is that the solution is hypotonic to the cell.