高一英語：三四單元重難點句型歸納二
3. Before she could move，she heard a loud noise. 她還沒有來得及動彈，就聽見很響的聲音。
However, before she could think twice, the water was upon her. 但還沒有回過身來，洪水便逼近了她。
該兩句中的before用作連詞，后接時間狀語從句。before用作連詞，接時間狀語從句時，表示“在……之前”。但在不同的語境中，往往有比較靈活的譯法。例如: He knocked me down before he saw me. 他差一點把我撞倒，才看到我。
【考例】The American Civil War lasted four years the North won in the end.
A. after B. before C. when D. then
[考查目標] 時間狀語從句的引導詞選擇。
[答案與解析]B before 表示“直到……”。
4. Tree after tree went down, cut down by the water, which must have been three meters deep. 洪水想必深達三米，樹一棵接一棵地倒了，被洪水沖斷了。
該句中的must have been表示推測。例如：You look so tired. You must have stayed up last night.
情態動詞may，might，most.can，could常用來表示推測。may，might，must多用在肯定句中，can，could多用在否定句和疑問句中。may，might，must，can，could后接動詞原形表示對現在的推測;may，might，must，can，could后接have done。表示對過去的推測。例如：
You may be a professor. / She must have met a fairy.
【考例】This cake is very sweet. You ____ a lot of sugar in it.
A. should put B. could have put
C. might put D. must have put
[考查目標] 情態動詞表示推測。
[答案與解析] D 前文說蛋糕很甜，由此可知一定是糖
放多了。對于過去的動作的推測應使用have done的
結構，所以應在B、D之間做選擇，又因為could have
done表示本可以做而沒有做，所以選擇D。
(責任編輯：康彥林)
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