What characterizes a hypotonic solution in relation to surrounding cells?

A hypotonic solution is characterized by having fewer particles, or solutes, compared to the surrounding cells. When a cell is placed in a hypotonic solution, the concentration of solutes outside the cell is lower than the concentration of solutes inside the cell. This difference leads to water moving into the cell in an attempt to balance the solute concentrations, often resulting in the cell swelling and potentially bursting due to the influx of water.

The focus of this question is on the osmotic pressure differences that define hypotonic conditions. In contrast, a solution with more particles than the cells would be hypertonic, causing cells to lose water and shrink. A solution with an equal number of particles would be isotonic, where there is no net movement of water into or out of the cell, maintaining cell shape and size. The option about containing only solutes does not provide the necessary context regarding concentration in relation to the cells, making it less relevant in this scenario. Therefore, a hypotonic solution's defining feature is its lower particle concentration compared to surrounding cells.