The difference of molarity and molality is in the units:
Molarity is expressed in mol solute / L solution;
while Molality is expressed in mol solute / kg solvent
Since no other data is given, let us assume that the contribution of methanol on the total volume is negligible. So that,
Molality = (20.3 mol / L) (1 L / 0.858 kg)
Molality = 23.66 m
The closest answer is letter C. 23.7 m