A student is given a mixture of barium sulfate, copper (II) sulfate, and water. 

The table shows information about barium sulfate and copper (II) sulfate. 

Compound	Substance Solubility in water	State at room temperature
Barium sulfate	insoluble	Solid
Copper (II) sulfate	soluble	solid

 How does the student obtain copper (II) sulfate crystals from the mixture? 

Filtration uses filter paper or fine porous ceramic to separate an insoluble solid from a liquid. And Crystallization is based on the difference in the solubilities of the components in a common solvent. Using this method, pure solid is obtained in form of crystals while impurities remain dissolved in the solvent.

Now, the given mixture has barium sulphate and copper (II) sulphate in water. Out of them, barium sulphate is insoluble in water while copper (II) sulphate is soluble in water.

Hence, solid barium sulphate will be separated from the mixture solution by filtration. Thus, barium sulphate is obtained as a solid while the filtrate has soluble copper sulphate. This copper (II) sulphate can be extracted from the filtrate solution by the process of crystallization.

Hence, the correct option is (D).