When the company released its flagship product in 1988, they had already built a worldwide distribution system comprising six geographical regions based on customer demand for its existing catalogue.
(A)
they had already built a worldwide distribution system comprising six geographical regions based on customer demand for
Incorrect(B)
they already had built a worldwide distribution system comprising six geographical regions that was based on customer demand made of
Incorrect(C)
they already had built a worldwide distribution system that comprised six geographical regions based on demand by customers for
Incorrect(D)
it had already built a worldwide distribution system that comprised six geographical regions based on customer demand for Correct(E) it already had built a worldwide distribution system comprising six geographical regions
being based on customer demand
it had for
IncorrectPOE -
the company singular, they plural
eliminate A, B & C
E - double had and being uses wrong
So, Answer D