白勇<语法全解>159页29题

29. 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

这道题在白勇语法全解的128页也出现过，两次我都做错了。我选了C，答案是B，一直想不明白，请nn帮忙解释一下。

once从句前半段是一般过去时，为什么这里可以用过去完成时？3x

C里面没有系动词啊...

and连接的两个部分,要讲究对称,不可能前面是was demonstrated而后面直接加个过去分词做形容词proved.

所以这里的proved应该和系动词连用与前面对称.