Explanation:

The solubility of copper sulfate in water is 1g/5mL, meaning 1 gram of copper sulfate can completely dissolve in 5 mL of water at a given temperature. The student adds only 780 mg (0.78 g) of copper sulfate in 5 mL of water, which is less than the maximum solubility limit (1g). Since the amount of solute added is less than what the solvent can dissolve, the solution prepared is unsaturated.

In an unsaturated solution, more solute can still dissolve in the given amount of solvent under the same conditions. Hence, the student’s solution is not saturated, concentrated, or incomplete.