Sentence Correction

With cloning technology, scientists are approaching
what has long been the ultimate goal of modern
husbandry: achieving a consistency of quality and
production in farm animals as once thought to be
limited to manufactured goods.
(A) achieving a consistency of quality and production
in farm animals as once thought to be
(B) achieving farm animals with a consistency of
quality and production as were once thought of as
(C) achieving in farm animals a consistency of
quality and production that was once thought to be
(D) achievement of farm animals whose consistency
of quality and production are the same as what were
once thought to he
(E) achievement of farm animals at a consistency of
quality and production once thought of as

why is A wrong?

OA is C