The ketone shown is heated with excess iodine in aqueous NaOH and the mixture is then acidified. Which structure is the organic acid obtained?

The drawn compound is pentan-2-one, a methyl ketone. The CH3 is tri-iodinated, hydroxide cleaves the CI3 group (as CHI3) and leaves the carboxylate of the remaining chain, three carbons plus the carbonyl carbon = butanoate; acidification gives butanoic acid. The trihalo ketone (D) is only an intermediate.