The correct option is D During boiling, composition of mixture remains constant
Liquid mixture of two miscible liquids which distill over without changes in composition is known as azeotropic mixture.
It is a mixture of two miscible liquids. It boils at constant temperature. During boiling, the composition in both liquid phase as well as vapour phase remains constant.
Azeotropic mixtures are formed by non ideal solutions.
As azeotropic mixture boils at a constant temperature, it cannot be separated by distillation methods because distillation works on the principle of difference in boiling points of the components in the mixture.