Not until she arrived at the meeting room ____ she had forgotten to bring the document.A. she realizedB. did she realizeC. she did realizeD. does she realize

步骤 1：识别句子结构
句子的结构是 "Not until + 从句 + 主句"，这种结构表示“直到……才……”。从句部分是 "she arrived at the meeting room"，主句部分是 "she had forgotten to bring the document"。

步骤 2：确定主句的时态
主句 "she had forgotten to bring the document" 使用了过去完成时，表示在到达会议室之前她已经忘记了带文件。

步骤 3：确定主句的倒装结构
由于句子使用了 "Not until" 的结构，主句需要部分倒装。因此，主句的谓语动词 "realized" 需要提前到主语 "she" 之前，变成 "did she realize"。