请问WHERE ONCE 的用法！谢谢先

请问WHERE ONCE 的用法！谢谢先

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（A）

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

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