In the reaction sequence $2CH_3CHO$ $\xrightarrow{OH^{-}} A$ $\xrightarrow{\Delta} B$; the product $B$ is

Which of the following compounds gives a positive test with $2,4$-$DNP$ ($2$,$4$-dinitrophenylhydrazine)?
$(a)$ Acetone
$(b)$ Butan-$2$-one
$(c)$ Acetaldehyde
$(d)$ Formaldehyde

What is the product of the following reaction?

What will be the main product in the following reaction?
$C_6H_5CHO + CH_3CHO \xrightarrow{OH^-, \Delta} ?$

Isobutyraldehyde on reaction with formaldehyde and $K_{2}CO_{3}$ gives compound '$A$.' Compound '$A$' reacts with $KCN$ and yields compound '$B$,' which on hydrolysis gives a stable compound '$C$.' The compound '$C$' is .... .

Which of the following reagents will convert isobutyraldehyde to the corresponding acid?

$I. HNO_3$	$II. NH_2NH_2 / OH^-$
$III. 2[Ag(NH_3)_2]^+$	$IV. NaOH$