To identify the solute and solvent, we look at the physical states and proportions:

• Solvent: This is the substance present in a larger quantity and typically determines the physical state of the overall solution. In sodium amalgam, Sodium (Na) is the solid base.

• Solute: This is the substance dissolved in the solvent. Mercury (Hg) is unique because it is a liquid at room temperature.

• Solute (Mercury): Liquid

• Solvent (Sodium): Solid

Therefore, the correct choice is Option 3: Solute: liquid and Solvent: solid. This is a classic example of a liquid-in-solid solution.