求助一道白勇的SC

法兰克福来客

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.
B and its superiority over the horse had been
c and its superiority to the horse

问题集中在BC两个选项上，我选的是C,我觉得题干中proved 前省略了was，理由是和was demonstrated 并列，但是答案是B,可是B中用了过去完成时，我看不出来题干中有什么必要的理由用这个时态的。哪位牛牛帮忙解释一下。

小伊YSY

你答案弄错了吧，我记得答案应该是c，确实是was的省略，而且b里头，had been时态很奇怪

In choice C, the best answer, the main predication usefulness…was demonstrated is paralleled by superiority [was] proved, with [was] omitted as understood. In choices A and E, the prepositional phrase beginning with…violates this parallelism; in A, B, and E, the verb forms being, had been, and having been are not consistent with the simple past tense in was demonstrated. The phrase superiority over is unidiomatic in B and D: x is superior to y, not over y. D is also faulty because no function word, such as the conjunction and, grammatically connects its superiority… to the rest of the sentence.

这个是当时这道题的解释