XDF补充题，请求解释

(E) While once the union had acquiesced to the prejudices of its English-speaking members in its supporting of

the answer is A，but why?

我觉得选C，where引导地点状语从句,和意思不符

While once the union had acquiesced to the prejudices of its English-speaking members  in support of the imposition of an alien tax on immigrant workers, after 1897 the United Mine Workers made a determined effort to enlist Italians and Slavs in its ranks.

我们先看除去蓝色部分的句意：一旦联邦默认了他们通过支持一项针对移民工人的额外课税来表达他们对说英语的成员的偏见，1897年之后联合采矿工人们就决定努力让意大利人和斯拉夫人和他们成为一伙的。

by supporting 和 in support of 我觉得没有什么太大区别（当然，动词〉介词短语，但非硬伤），关键就是地点状语从句我觉得不对的啊，因为后一个分句根本没有提到地点的问题。因此看来这里的while用来介绍背景。

欢迎支持A的同学反驳我~！

這個題目有點怪耶，我覺得A跟C各有缺點,但是C的缺點是扭曲原意，因為had acquiesced to the prejudices of its English-speaking members by supporting 是指透過support xxx達到

承認這種偏見的存在，但是C卻是表達承認這種偏見以支持xxx的訂定.

我的看法是by supporting與in support of 的因果關係

所以如果依照上一樓講的意思,似乎不能選C囉...各人意見