Which of the following pairs of compounds can be distinguished by warming with $\mathrm{NaOH}/\mathrm{I}{}_2$?

In each of the first three pairs exactly one member has $\mathrm{CH}{}_3\mathrm{CO}{}^{-}$ or $\mathrm{CH}{}_3\mathrm{CH}(\mathrm{OH}){}^{-}$ (pentan-2-one, ethanol, butan-2-ol) and gives the yellow precipitate. Pentan-3-one and propanal both have neither group, so both give no precipitate and the pair is not distinguished.