Explanation

(c)
The Kolbe’s electrolysis proceeds $via$ free radical mechanism. For example, when sodium propionate is electrolysed, $n -$butane, ethane, ethylene are obtained. The propionate ion discharge at the anode to form free radicals.
$C_{2}H_{5}COO^{-} \rightarrow C_{2}H_{5}COO^{⦁} + e^{-}$
$C_{2}H_{5}{COO}^{⦁} \rightarrow C_{2}H_{5}^{⦁} + {CO}_{2}$
$2C_{2}H_{5}^{⦁} \rightarrow C_{4}H_{10}$
$C_{2}H_{5}^{⦁} + C_{2}H_{5}^{⦁} \rightarrow C_{2}H_{4} + C_{2}H_{6}$