Answer (D) :- Here $\frac{c}{d}$ could not be an integer
Given a = 6b = 12c
Let $\frac{a}{12}$ = $\frac{b}{2}$ = c = k
a=12k
b=2k
c=k...............................i
Similarly,
2b = 9d = 12e
Let $\frac{b}{18}$ = $\frac{d}{4}$ =$\frac{c}{3}$ =k
b=18k
d=4k
e=3k..............................ii
from i and ii we get
a=108k
b=18k
c=9k
d=4k
e=3k
Now, putting in option we get D) as ans.