In the above compound, the amine group is attached to the parent chain of 4 carbon atoms and an ethyl group is attached to N-atom of the amine group, thus the IUPAC name of the given compound is N-ethyl butan-1-amine.
(B) CH3−CH2−CH3|CH−NH−CH3
In the above compound, the amine group is attached to 2nd carbon atom of parent chain of 4 carbon atoms and one methyl group is attached to N-atom of amine group, thus the IUPAC name of the given compound is N-methyl butan-2-amine.