A mixture of two miscible liquids can be separated by provided the difference between their boiling points is atleast $25{}^0\text{C}$.

The correct option is C distillation
The method used for separating two miscible liquids present in a mixture that have sufficient difference in their boiling points i.e., at least $25{}^0\text{C}$ is distillation.
These liquids should boil without decomposition. In the process, their vapours are separately allowed to condense to form liquid.