Recrystallization of a solid is an experimental technique used to separate out impurities from a pure product using differential solubilities of the solids in a solvent at different temperatures. We chose a solvent in which the pure solid has lower solubility at low temperatures but is completely soluble at higher temperatures. The amount of solvent taken must be sufficient to completely dissolve the impure solid formed in a reaction. The impurities must be soluble in cold solvent, so that they can remain in solution after crystallization of pure compound. When the amount of solvent is too little then we cannot achieve the separation of pure crystals as the pure solid crystallizes on the impurities.
So the correct answer will be the crystals form with product coated onto impure crystals