请教一语法题

(Where once the union had acquiesced to the prejudices of its English-speaking members by supporting) 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.
a)Where once the union had acquiesced to the prejudices of its English-speaking members by supporting
b)Where once the union acquiesced to its English-speaking members' prejudices for the support of
c)While once the union had acquiesced to the prejudices of its English-speaking members in support of
d)While once the union acquiesced to its English-speaking members' prejudice in supporting
e)While once the union had acquiesced to the prejudices of its English-speaking members in its supporting of

谁能翻译一下这个句子，并告知它的结构？