Which one is not equal to zero for an ideal solution?

For an ideal solution,
(A) The volume of mixing is zero. ΔVmix=0
(B) The observed pressure is equal to the pressure calculated from Raoult's law, then the solution is said to be an ideal solution. Pobserved=PRaoult ΔP=Pobserved−PRaoult=0
(C) The enthalpy change of mixing is zero ΔHmix=0
(D) But the entropy of mixing is not equal to zero. ΔSmix≠0. Option D is correct.