Aniline reacts with which of these to form a Schiff base?

An amine on reaction with benzenesulphonyl chloride produces a compound insoluble in alkaline solution. This amine can be prepared by ammonolysis of ethyl chloride. The correct structure of the amine is:

Product $(B)$ in this reaction is

Which one among the following statements is true?

Consider the molecule $1,3-dimethyl-1,2,3,4-tetrahydroquinoxaline$ with an amino group at the $5$-position. Upon protonation,which nitrogen atom is the most basic and will be protonated first? Identify the correct structure of the product '$A$' formed after protonation.

Which of the following amines has the lowest $pK_{b}$ value?