885 section 10-15

15.   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（C）

(E) with its superiority to the horse having been

 选 c的话为什么不需要在后面加一个was,demonstrated前面就有呀,这里不是也要有吗?

可以省略的。