Which of the following is formed when benzaldehyde reacts with concentrated sodium hydroxide?

Cyclopentanone $\xrightarrow[\text{traces of } KOH]{HCN} A$ $\xrightarrow{LiAlH_4} B$ $\xrightarrow{NaNO_2, HCl} C$
$C$ is

Arrange the following compounds in order of decreasing reactivity for nucleophilic addition reaction:
$(I)$ $CH_3COCH_2Cl$
$(II)$ $ClCH_2CHO$
$(III)$ $HCHO$
$(IV)$ $CH_3COCH_3$

Give the reactivity order towards $HCN$ for the following compounds:
$(I)$ $Ph-CO-CH_3$
$(II)$ $CH_3-CO-CH_3$
$(III)$ $CH_3-CHO$
$(IV)$ $Ph-CO-CH_2-CH_3$

Acetaldehyde and acetone can be distinguished by

Identify the major product $A$ in the following reaction:
[Image of the reaction: $A$ substituted tetralin derivative with a ketone group,a chlorine atom,and a nitro group,reacting with $N_2H_4/KOH/H_2O$ (Wolff-Kishner reduction)]