c) the solute molecules adhere to the polar regions of the water molecules so there is no room for more sucrose molecules
Explanation:
A solution contains a solvent (water in this case) and a solute (sucrose in this case). A solution can either be saturated or unsaturated depending on whether it can still dissolve a solute or not.
According to this question, the 0.7 M sucrose solution does not dissolve the sucrose (solute) any longer. This implies that the sucrose solution is getting SATURATED. The saturation of the sucrose solution occurs because the amount of solutes is equating the amount of solvent in the solution.
The solubility of a solution depends upon polarity. The solute molecules (sucrose) adhere to the polar regions of the water molecules (solvent). When this occurs to the point where no other sucrose molecule can adhere, the solution becomes SATURATED so there is no room for more sucrose molecules.
