While we were cleaning up the classroom, the staff were having a meeting.

当我们正在打扫教室时，职员们正在开会。

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While we were cleaning the street, a stranger came up to ask the way.

当我们在清扫大街的时候，一个陌生人走上来问路。

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While we were cleaning the street, a stranger came up to ask the way.

当我们在清扫大街的时候，一个陌生人走上来问路。

youdao