If a de-shelled egg gains weight after being soaked in sucrose solution, what term best describes this solution?

The correct answer would be - hypotonic solution.

Explanation:

The egg cell contains more solute than the sucrose solution  which makes the sucrose solution a hypotonic or low solute solution. Hypotonic solution is a solution that has low concentration of the solutes than the another solution. This tye of case leads to the movement of the water to, move in the area of high concentration of solutes.

In this case the water will move in to the egg and swell the egg due to the diffusion of water through semipermeable membrane from low solute area to high solute area.