例句：
有人曾经认为铅可以变成黄金。
It was once thought that lead could be transmuted into gold.
人们曾经认为地球是平的。
People used to think the earth was flat.
我曾经在伦敦居住过。
I used to live in London.
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2021-09-14
例句：
有人曾经认为铅可以变成黄金。
It was once thought that lead could be transmuted into gold.
人们曾经认为地球是平的。
People used to think the earth was flat.
我曾经在伦敦居住过。
I used to live in London.