The correct option is D Kraft temperature
a) Critical temperature (Tc) is a minimum temperature above which gas cannot be liquified, Tc = 8a27Rb
b) Inversion temperature (Ti) is the temperature at which Joule - Thomson effect changes sign, Ti=2×Tb
c) Reduced temperature (θ)
θ = TTc
d) Kraft temperature (Tk)
The formation of micelles takes place only above a particular temperature called Kraft temperature.