cloning technology

[GmatKiss]

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 be
(E) achievement of farm animals at a consistency of quality and production once thought of as

OA is C. What's problem with A
Need experts help!!

[gmatblood]

good one! waiting for experts to comment.

[1947]

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 be
(E) achievement of farm animals at a consistency of quality and production once thought of as

OA is C. What's problem with A
Need experts help!!

Even I picked A.....i think problem with A is "as once thought to be "
Experts can explain why is this wrong