The correct answer is option A, that is, the mass of the solute.
Before, preparing the solution, the laboratory technician needs to measure the mass of the solute. In the given question, the molarity of NaOH is given, the volume of the solution is given, the molar mass of NaOH is 40 g/mol.
As one knows the molarity of the solute, the volume of the solution, and the molar mass of the solute, thus, there is a need to determine only the mass of the solute prior of preparing the solution.
