Explanation

(c)
Tollen’s reagent, Fehling solution and ${\frac{NaOH}{NaI/}H}^{+}$ are not able to change butan-2-one (ketone) into propanoic acid because these are mild oxidising agents, so $NaOH/I_{2}$ firstly from iodoform along with $C_{2}H_{5}COONa$ with butan-2-one (ethyl methyl ketone). In these $C_{2}H_{5}COONa$ reacts with acid ($H^{+}$) to give $C_{2}H_{5}COOH$ (propanoic acid).
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ O$
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$CH_{3} - C - CH_{2} - CH_{3} + 3I_{2} + 4NaOH$
butan-2-one
(ethyl methyl ketone)
$\ \ \ \ \ \ \ \ \ \ \ \ \rightarrow CHI_{3} \downarrow + C_{2}H_{5}COONa + 3NaI + 3H_{2}O$
iodoform
$C_{2}H_{5}COONa + H^{+} \rightarrow C_{2}H_{5}COOH + Na^{+}$
Propanoic acid