Which of the following give a yellow precipitate of iodoform on warming with $\mathrm{I}{}_2$ and aqueous $\mathrm{NaOH}$?

Ethanol and propan-2-ol contain the $\mathrm{CH}{}_3-\mathrm{CH}(\mathrm{OH}){}^{-}$ unit, which is oxidised to $\mathrm{CH}{}_3\mathrm{CHO}$ or $\mathrm{CH}{}_3\mathrm{COCH}{}_3$ and then undergoes the haloform reaction. Pentan-3-one has no $\mathrm{CH}{}_3\mathrm{CO}$ group and butan-1-ol no $\mathrm{CH}{}_3\mathrm{CH}(\mathrm{OH})$ unit.