In which of the following sets, reactant and reagent are correctly matched to get corresponding carboxylic acid?
\[
\begin{array}{ll}
\textbf{I.} & \mathrm{CH_3CH_2CH_2OH}
\;\xrightarrow{\mathrm{CrO_3,\ H_2SO_4}}\; ? \\[2mm]
\textbf{II.} & \mathrm{CH_3CH_2CH_2Br}
\;\xrightarrow{\mathrm{CO,\ H_3O^+}}\; ? \\[2mm]
\textbf{III.} & \mathrm{CH_3CHO}
\;\xrightarrow{\mathrm{KMnO_4/OH^-,\ H_3O^+}}\; ?
\end{array}
\]
The correct answer is
