The product formed from the following reaction sequence is :

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

An optically active compound $C_6H_{12}O$ gives a positive test with $2,4-$dinitrophenylhydrazine,but a negative test with Tollens' reagent. What is the structure of the compound?

Match the reactions in Column $I$ with appropriate options in Column $II$.

Column $I$	Column $II$
$A$. $Ph-N_2Cl + Ph-OH \xrightarrow{NaOH/H_2O, 0^{\circ}C} Ph-N=N-Ph-OH$	$p$. Racemic mixture
$B$. $Pinacol \xrightarrow{H_2SO_4} Pinacolone$	$q$. Addition reaction
$C$. $Ph-CO-CH_3 \xrightarrow{1. LiAlH_4, 2. H_3O^+} Ph-CH(OH)-CH_3$	$r$. Substitution reaction
$D$. $4-chlorocyclohexanethiol \xrightarrow{Base} Thiacycloheptane$	$s$. Coupling reaction
	$t$. Carbocation intermediate

The major product of the following reaction is

Which of the following compounds is responsible for the iodoform reaction?