(A) $$\rightarrow$$ (R) Charcoal treatment: Activated charcoal has a highly porous surface that readily adsorbs colored organic impurities from a solution.(B) $$\rightarrow$$ (P) Steam distillation: o-Nitrophenol undergoes intramolecular hydrogen bonding (making it volatile), whereas p-nitrophenol forms intermolecular hydrogen bonds (making it less volatile). Because of this difference in volatility, they can be separated easily via steam distillation.(C) $$\rightarrow$$ (Q) Fractional distillation: Crude naphtha is a complex mixture of hydrocarbons obtained from petroleum refining, where components have close boiling points and are separated using fractional distillation.(D) $$\rightarrow$$ (S) Distillation under reduced pressure: Glycerol has a very high boiling point and tends to decompose at or near its boiling temperature. Lowering the external pressure reduces its boiling point, allowing it to distill safely without decomposing.
$$\text{(A)-(r), (B)-(p), (C)-(q), (D)-(s)}$$