Sugar is added to a cup of water. Here, sugar is the _____.

The correct option is A solute
Solvent and solute are the components of a solution, out of which solute is generally present in a smaller quantity while the solvent is generally present in a larger quantity. In a solution, the solute gets completely dissolved in the solvent.

Sugar when mixed in water gets completely dissolved in it. Here, sugar is the solute, water is the solvent, and sugar water is the solution.