Sentence Correction

In a previous design. the weight of the discus used in
track competition is concentrated in a metal center.
but now it is lined with lead around the perimeter,
thereby improving stability in flight and resulting in
longer throws.
696

(A) In a previous design, the weight of the discus
used in track competition is concentrated in a
metal center, but now it is

(B) According to a previous design, the weight of
the discus used in track competition was
concentrated in a metal center, but now it is

(C) Once designed with its weight concentrated in a
metal center, the discus used in track
competition is now

(D) The discus used in track competition, once
designed with its weight concentrated in a metal
center, but now

(E) The discus used in track competition was once
designed having its weight concentrated in a
metal center and now

IMO C.

designed in past tense.

"weight is concentrated in a metal center"

"discus is lined with lead"

IMO C