动词短语
中文翻译：偶然发现
同义词：
['happen upon', 'come across例句：1. I fell on this book in the library and decided to read it.（我在图书馆偶然发现了这本书，决定读一读。）']
例句：
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1. I fell on this book in the library and decided to read it.
我在图书馆偶然发现了这本书，决定读一读。
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2.He fell on the job unexpectedly when his boss left for a business trip.
老板出差时，他突然被派去工作了。
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3.She fell on her knees and prayed for forgiveness.
她跪下来祈祷宽恕。