Identify the product $B$ in the following reaction:
$C_6H_5NH_2$ $\xrightarrow[0^\circ-5^\circ C]{NaNO_2/HCl} A$ $\xrightarrow{Ph-N(CH_3)_2} B$

$A$ hydrocarbon $'A'$ $(C_4H_8)$ on reaction with $HCl$ gives a compound $'B'$ $(C_4H_9Cl)$,which on reaction with $1 \ mol$ of $NH_3$ gives compound $'C'$ $(C_4H_{11}N)$. On reacting with $NaNO_2$ and $HCl$ followed by treatment with water,compound $'C'$ yields an optically active alcohol,$'D'$. Ozonolysis of $'A'$ gives $2 \ mols$ of acetaldehyde. Identify compounds $'A'$ to $'D'$. Explain the reactions involved.

Match the following:

List-$I$ (Amine)	List-$II$ ($pK_b$ value)
$A$. $N,N$-Dimethylaniline	$I$. $9.30$
$B$. Aniline	$II$. $8.92$
$C$. $N$-Ethylethanamine	$III$. $9.38$
$D$. $N$-Methylaniline	$IV$. $3.00$

The correct answer is

Which one of the following methods is neither meant for the synthesis nor for separation of amines?

The incorrect statement regarding the reaction shown below is:

Which of the following chemicals are responsible for the production of methyl isocyanate,which caused the Bhopal gas tragedy?