By the mid-seventeenth century, Amsterdam had
built a new town hall so large that only St. Peter’s in
Rome, the Escorial in Spain, and the Palazza Ducale
in Venice could rival it for scale or magnificence.
(A) could rival it for
(B) were the rivals of it in their
(C) were its rival as to
(D) could be its rivals in their
(E) were rivaling its

Can someone please explain why C is incorrect and A is correct