d
A doubly bonded carbon atom having an alkyl group is oxidised to aldehyde which is further oxidised to carboxylic acid.

\(C{{H}_{3}}C{{H}_{2}}CH=CHC{{H}_{3}}\xrightarrow[(ii)\,{{H}^{+}}]{(i)\,KMn{{O}_{4}},O{{H}^{-}}}\) 

\(\begin{matrix}
   C{{H}_{3}}CHO  \\
   \downarrow   \\
   C{{H}_{3}}COOH  \\
\end{matrix}\) \(+\) \(\begin{matrix}
   C{{H}_{3}}C{{H}_{2}}CHO  \\
   \downarrow   \\
   C{{H}_{3}}C{{H}_{2}}COOH  \\
\end{matrix}\)