(D)

All these variables, except for the freezing point of the solute, are needed to calculate molar mass from freezing-point depression.

Molar mass can be calculated from the relationship for freezing-point depression:

D T of the solution = molality of solute X kf of the solution

Once the molality is calculated, then the number of moles of unknown solute can be found because they equal the molality of the solution X kg solvent.

Finally, the molar mass of the unknown solute can be found by dividing the moles of the solute into the mass of the solute.