Salt can be separated from its solution (salt dissolved in water), because
(a) mixing of salt in water is a change that can be reversed by heating and melting of salt.
(b) mixing of salt in water is a change that cannot be reversed.
(c) mixing of salt in water is a permanent change.
(d) mixing of salt in water is a change that can be reversed by evaporation.
Salt can be separated from its solution (salt dissolved in water), because mixing of salt in water is a change that can be reversed by evaporation.
Salt can be separated from water solution by evaporating the water. Hence mixing of salt in water is a reversible change.
Hence option (D) is correct.