Explanation

(b)
Boiling point and freezing point depend on $k_{b}$ (molal elevation constant) and $k_{f}$ (molal depression constant) of the solvent. Thus, equimolar solution (of the non-electrolyte) will have same boiling point and also same freezing point.
$\mathrm{\Delta}T_{f} = k_{f} \times molality$
$\mathrm{\Delta}T_{b} = k_{b} \times molality$
Note In this question nature of salute has not been mentioned. Hence, we have assumed that solute is non-electrolyte.