(A) :If two liquids on mixing form a solution with liberation of heat, it is a non ideal solution with negative deviation.
(R) : Solutions with negative deviation are accompanied by decrease in volume.

A non-ideal solution that departs from the circumstances of an ideal solution, in which molecular interactions are identical to or very similar to those between molecules of various components. If a solution deviates in either a positive or negative direction from Raoult's law, it is said to be a non-ideal solution.
Positive divergence from the ideal solution: the total vapour pressure is higher than what Raoult's equation predicts. Solute-solvent (A-B) interactions are weaker as compared to interactions between pure components (A-A or B-B). The mixture's enthalpy changes in a way that increases volume.
For instance, acetone and ethanol, acetone and carbon disulfide, acetone and benzene, etc.
Hence, correct option is: (A) Both (A) and (R) are true  and (R) is correct explanation of (A)