Once the economic and social usefulness of the motor car was demonstrated and with its superiority to the horse being proved, much of the early hostility to it in rural regions disappeared.
(A) and with its superiority to the horse being
(B) and its superiority over the horse had been
(C) and its superiority to the horse
(D) its superiority over the horse
(E) with its superiority to the horse having been

is 'was' not needed at the end of choice C?