$A \xrightarrow{} (CH_3)_2C=CH-CO-CH_3$. $A$ is:

The compound formed by the reaction of ethanal with semicarbazide contains $.....................$ number of nitrogen atoms.

Which one of the following compounds does not give a primary alcohol on reduction?

The increasing order of the reactivity of the following compounds in nucleophilic addition reaction is:
Propanal,Benzaldehyde,Propanone,Butanone

Two compounds $A$ and $B$ with the same molecular formula $(C_{3}H_{6}O)$ undergo Grignard's reaction with methylmagnesium bromide to give products $C$ and $D$. Products $C$ and $D$ show the following chemical tests.

Test	$C$	$D$
Ceric ammonium nitrate Test	Positive	Positive
Lucas Test	Turbidity obtained after five minutes	Turbidity obtained immediately
Iodoform Test	Positive	Negative

$C$ and $D$ respectively are:

Consider the following sequence of reactions:
$Benzene$ $\xrightarrow{CO, HCl, \text{anhydrous } AlCl_3/CuCl} A$ $\xrightarrow{B, OH^-, 293 K} \text{Chalcone (1,3-diphenylprop-2-en-1-one)}$
The substance $B$ is: