Aromatic primary amine when treated with cold $HNO_2$ gives

$A$ hydrocarbon $A$ $(C_{4}H_{8})$ on reaction with $HCl$ gives a compound $B$ $(C_{4}H_{9}Cl)$ which on reaction with $1 \ mol$ of $NH_{3}$ gives compound $C$ $(C_{4}H_{11}N)$. On reacting with $NaNO_{2}$ and $HCl$ followed by treatment with water,compound $C$ yields an optically active compound $D$. The compound $D$ is

Which of the following has the highest value of $pK_b$?

Arrange the following in increasing order of their basic strength:
$(i)$ $C_2H_5NH_2, C_6H_5NH_2, NH_3, C_6H_5CH_2NH_2$ and $(C_2H_5)_2NH$
$(ii)$ $C_2H_5NH_2, (C_2H_5)_2NH, (C_2H_5)_3N, C_6H_5NH_2$
$(iii)$ $CH_3NH_2, (CH_3)_2NH, (CH_3)_3N, C_6H_5NH_2, C_6H_5CH_2NH_2$

In the reaction sequence $A$ $\xrightarrow{Sn/HCl} B$ $\xrightarrow{HNO_2, 0^{\circ}C} C$ $\xrightarrow{C_2H_5OH} C_6H_6$,identify the functional groups present in $A, B,$ and $C$.

Predict the reagents or products $(1)$ to $(5)$ in the following reaction sequence:
$p-Nitrotoluene$ $\xrightarrow{(1)} p-Toluidine$ $\xrightarrow{(CH_3CO)_2O/\text{Pyridine}} p-Acetotoluidide$ $\xrightarrow{HNO_3/H_2SO_4} (2)$ $\xrightarrow{(3)} (4)$ $\xrightarrow{(5)} 3-Nitrotoluene$