Final answer:
The temperature required to freeze a solution is a) lower than the freezing point of the pure solvent due to vapor pressure lowering.
Step-by-step explanation:
Vapor pressure lowering occurs at all temperatures, resulting in the temperature required to freeze the solution being lower than the freezing point of the pure solvent. When a solute is dissolved in a solvent, this results in a decrease in the solution’s vapor pressure compared to the pure solvent. As illustrated in phase diagrams, this is depicted as the solid-liquid curve for the solution being displaced left of that for the pure solvent, which indicates a freezing point depression. Therefore, the correct answer to the student's question is that the temperature required to freeze the solution is a)lower than the freezing point of the pure solvent.