题目内容
20．After having checked all the windows and doors were closed and________ all the lightswere turned off，the teacher left the Classroom．（ ）
| A． | what | B． | that | C． | how | D． | why |
分析 检查完门窗都关好了，所有的灯也都关了后，老师离开了教室．
解答 答案：B
题干中all the windows and doors were closed 和all the lights were turned off都充当动词check的宾语；宾语从句中的连词that通常可以省略，但为了避免歧义时，不可省略．故选B．
点评 本题考查了宾语从句中连词that的特殊用法．宾语从句中连词that通常可以省略，但如果引起歧义则不能省略．本题如果省略了that句意就有了两种解释：一种是all the windows and doors were closed 和all the lights were turned off都充当动词check的宾语；另一种是After having checked all the windows and doors were closed和all the lights were turned off并列，很明显句意就错误了．
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