The compound which on reaction with aqueous nitrous acid $(HNO_2)$ at low temperature produces an oily nitrosoamine is

Among the following,the strongest base is

The number of secondary amines with the molecular formula $C_4H_{11}N$ is

Consider the following sequence of reactions:
$C_6H_5NH_2$ $\xrightarrow{NaNO_2, 0-5^{\circ}C} 'A'$ $\xrightarrow{N,N-\text{Dimethylaniline}} 'B'$
The product $B$ is

The major product in the following reaction is:

The reaction of aniline with chloroform under alkaline conditions leads to the formation of