Explanation

(b)
Aldehydes, which have no $\alpha -$hydrogen atom, undergo Cannizaro reaction is presence of conc. $NaOH$ and yield an alcohol and an acid salt. (Disproportionation).
$2C_{6}H_{5}CHO\overset{\ \ NaOH\ \ \ \ }{\rightarrow}C_{6}H_{5}CH_{2}OH + C_{6}H_{5}COONa$
benzaldehyde benzyl alcohol