问题
选择题
Not until the press reported the pollution _________ why the water supply had been cut off.
A．people did know
B．people had known
C．did people know
D．had people known
答案
答案：C
题目分析：not until 位于句首，句子使用部分倒装。排除ＡＢ，Ｄ答案时态不对。句意：
直到新闻报道了污染人们才知道为什么水的供应被切断。
点评：倒装分为部分倒装和完全倒装。要分清他们的概念及使用规则。部分倒装是把部分谓语（ｂｅ动词／助动词／情态动词）提到主语前面，完全倒装是把整个谓语提到主语前面。