When protoplasts are placed in distilled water, they experience endosmosis. This means water moves into the protoplasts due to the osmotic gradient: the concentration of solutes inside the protoplasts is higher than in the surrounding distilled water.

As water enters the protoplasts, they begin to swell. Because protoplasts (plant cells without their cell wall) have only the plasma membrane to contain the cell's contents, they eventually cannot withstand the internal pressure caused by the water influx, leading them to burst.

The kinetics of this process can be represented graphically. The correct graph option shows an initial slow increase in swelling followed by a rapid increase just before bursting. This is typically represented by a sigmoidal or S-shaped curve where the reaction initially is slow, increases rapidly, and then levels off as the protoplasts burst. Hence, it represents a process of accumulation leading to a critical point (burst).

The correct option is:

This graph adequately demonstrates the rate of swelling and bursting over time due to endosmosis in a hypotonic solution like distilled water.