什么叫逻辑主语？
逻辑主语是相对于语法主语而言的。逻辑主语这一概念主要用在非谓语动词(或称动词的非限定形式)上。非谓语动词是指动词不定式、分词和动名词。
A. 动词不定式的逻辑主语：
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It is impossible for us to go by plane. 我们坐飞机去是不可能的。
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For us to take part in the discussion would be a conflict of interest. 我们要是参加讨论，就会造成利害的冲突。
B. 分词的逻辑主语：
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It being a holiday, I went fishing. 那天是假日，我钓鱼去了。
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The job finished, we went home straight away. 工作结束后,我们马上回家了。
C. 动名词的逻辑主语(用名词的所有格或普通格,用代词的所有格或宾格):
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Wesley's returning so soon surprised us. (UGE) 韦斯利回来这么早,很令我们吃惊。
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I didn't know about the weather being so awful in this area. (CGEL) 我不知道这一地区的天气这么糟。
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They liked our singing. (CGEL) 他们喜欢我们唱歌。
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They liked us singing. (CGEL) 他们喜欢听我们唱歌。
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She thought of her mother singing her to sleep at night, of her father giving her rides on his shoulders, and of her grandmother and younger brother smiling at her with their fervent green eyes. (Dan Brown, The Da Vinci Code) 她回想起了妈妈唱歌哄她入睡的情景；回想起了骑在爸爸肩上玩耍的时光；回想起了祖母和弟弟用绿色的眼睛看着她，冲她微笑的
样子。(《达·芬奇密码》)
此外，逻辑主语的概念也用在下列独立结构上。
A. 名词(或代词) + 形容词:
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His face pale with rage, Borg rose to address the group. (UGE) 博格气得脸色发白，站起来向大家讲话。
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He sat in the front row, his mouth half open... 他坐在前排，嘴半张着……
B. 名词(或代词) + 副词:
Dinner over, we decided to play bridge. 吃过饭后,我们决定打桥牌。
C. 名词(或代词) + 介词短语:
In half an hour Delia came, her right hand in a bandage. 半小时后，迪莉娅回来了，她右手缠着绷带。