The value of Trouton's ratio $$\left( {\frac{{{\lambda _{\text{b}}}}}{{{{\text{T}}_{\text{b}}}}}} \right)$$  for a number of substances is 21 (where, $${{\lambda _{\text{b}}}}$$ = molal that of vaporisation of a substance at its normal boiling point, kcal/kg.mole and T_b = normal boiling point, °K). The Kis-tyakowsky equation is used for calculation of Trouton's ratio of __________ liquids.

A. Polar

B. Non-polar

C. Both A & B

D. Neither A nor B

Answer: Option C