In the given example B,C and B,D are :
(a) CH3−CH2−CH2−CH2NH2
Butanamine (1o)
(b) CH3−CH2−NH2|CH−CH3
Butan-2-amine (1o)
(c) CH3−CH3|CH−CH2−NH2
2-Methylpropanamine (1o)
(d) CH3−CH3|C|−CH3NH2
2-methylpropan-2-amine (1o)
(e) CH3−CH2−CH2−NH−CH3
N-methylpropanamine (2o)