at which point cp=cv for real gases? options i.absolute zero ii.triple point iii.critical point

As we already know that :

Cp - Cv = -T * (dS/dV)_T * (dS/dP)_T

For Absolute Zero : A perfect crystal at Absolute Zero (0K) has Entropy (S) = 0 and according to the equation Cp - Cv tends to Zero, That''s Why : Y = (Cp/Cv) = 1

For Triple Point :  Cp - Cv not equals to zero

For Critical Point : At the critical point, gamma would be infinite.