Which of the following gives a yellow precipitate on warming with $\mathrm{I}{}_2$/$\mathrm{NaOH}$?

The iodoform test needs the $\mathrm{CH}{}_3-\mathrm{CH}(\mathrm{OH}){}^{-}$ unit (or $\mathrm{CH}{}_3\mathrm{CO}{}^{-}$ after oxidation by hypoiodite). Only propan-2-ol, $\mathrm{CH}{}_3\mathrm{CH}(\mathrm{OH})\mathrm{CH}{}_3$, has it, so it is oxidised to propanone and then gives yellow $\mathrm{CHI}{}_3$. The other three lack the $\mathrm{CH}{}_3\mathrm{CH}(\mathrm{OH}){}^{-}$ group.