问题描述:
_____ recently _____ scientists known something about AIDS.
[A]Not until…have [B] Until…did [C] Not until…do [D] Until…have
解释为什么
翻译整句
[A]Not until…have [B] Until…did [C] Not until…do [D] Until…have
解释为什么
翻译整句
问题解答:
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