With respect to entropy, freezing point of a solvent decreasel with increasing solute concentration because, as compared to the fusion of pure solvent,

a the entropy of the "liquid phase" decreases, the entropy of the solid phase remains the same, and thus the absolute value of the negative entropy change for the process decreases, requiring a lower temperature to maintain the same thermodynamic favorability for this enthalpically driven process.

b the entropy of the "liquid phase" decreases, the entropy of the solid phase remains the same, and thus the absolute value of the negative entropy change for the process decreases, requiring a lower temperature to maintain the same thermodynamic favorability for this entropically driven process.

c the entropy of the "liquid phase" increases, the entropy of the solid phase remains the same, and thus the absolute value of the negative entropy change for the process increases, requiring a lower temperature to maintain the same thermodynamic favorability for this entropically driven process.

d the entropy of the "liquid phase" increases, the entropy of the solid phase remains the same, and thus the absolute value of the negative entropy change for the process increases, requiring a lower temperature to maintain the same thermodynamic favorability for this enthalpically driven process.