What would most likely happen to a unicellular organism if it was exposed to a hypotonic solution for an extended period of time? it would shrivel and shrink. it would swell but never burst. it would swell and then burst. it would not be affected.

The correct option is It would swell and then burst.

Hypotonic solution is the one which contains low concentration of solute outside the cell than the inside. It means that the concentration of the solvent ( which is water) is more outside the cell as compared to inside.  

Water always moves from high concentration of solvent to low concentration. When a unicellular organism is exposed to hypotonic solution, water will move inside the organism. If this happens for an extended period of time, the unicellular organism would swell and then burst.

Thus, the correct answer is It would swell and then burst.