In the reaction $CH_3CHO + HCN \to CH_3CH(OH)CN$,a chiral centre is produced. This product would be

The product $(4)$ in the given reaction sequence is:

$3$-hydroxybutanal is formed when $(X)$ reacts with $(Y)$ in dilute $(Z)$ solution. What are $X, Y$ and $Z$?

The reagent$(s)$ which can be used to bring about the following transformation is(are):
$(A)$ $LiAlH_4$ in $(C_2H_5)_2O$
$(B)$ $BH_3$ in $THF$
$(C)$ $NaBH_4$ in $C_2H_5OH$
$(D)$ Raney $Ni / H_2$ in $THF$

$PCl_5$ reacts with propanone to give:

Acetaldehyde cannot show: