Do not just write "a", "b", or "c". Use the correct terms to describe their relationship.
a)
CH3-CH2-CH2-CH-CH3
and
CH3-CH-CH2-CH3
CH3
CH3
b) CH3-CH2-CH2-CH2-CH3
and
CH3-CH-CH3
CH2
CH3
c)
CH3-CH2-CH2
and
CH3-CH2-CH3
CH3
CH3
CH3-CH-CH2-CH3
CH3
C
-CH3
and
CH3
d)
CH3