Step 1 - Understanding what is a solution
A solution is a homogeneous mixture consisting of two or more substances: one solvent and two or more solutes. Even though water is the commonest of all solvents, it is not the only one. Alcohol can be a solvent as well, for example.
The solvent is usually defined as the substance present in the greatest amount.
Step 2 - Answering the question
The correct answer is item c) solvent, since the solvent is usually present in the greatest amount.