Amines Part 1

The amine on reaction with benzene sulphonyl chloride (Heisenberg reagent) produces a compound insoluble in alkali. It indicates the amine is a 2∘ amine. i.e. all options are possible except option (b) which is a 1∘ amine (CH3CH2NH2).
As this 2∘ amine can be prepared by ammonolysis of ethyl chloride, the 2∘-amine should have at least one ethyl (C2H5) group.
(a) Ph−NH−CH2CH2CH3 does not have ethyl group.
(c) CH3CH2CH2−NH−CH3 does not have ethyl group.
(d) CH3CH2CH2−NH−CH2CH3 has one ethyl group.
So, option (d) is the correct answer.
Preparation CH3CH2CH2−NH−CH2CH3 by ammonolysisof CH3CH2Cl