Pls help me understand this one correctly.

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 it English-speaking members’ prejudice 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