Trees help keep the air clean and they make oxygen that we can breathe.

树木有助于净化空气，释放出可供我们呼吸的氧气。

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Trees reduce dust and help keep the air clean.

树木减少灰尘，有助于保持空气清洁。

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They feed on tiny things in sea water and help to keep the water clean in the process.

它们以海水中的微小物体为食，并在这个过程中帮助保持海水的清洁。

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This can help a worker keep his nose clean or stay out of trouble.

VOA: special.2009.09.13

Mr Taylor said the landowners help keep the area clean and tidy.

BBC: NEWS | UK | Wales | North East Wales | Beach faces tide and untidyness

Businesses, which have included Microsoft, Marriott International and GlaxoSmithKline, create real-world challenges for students to solve, such as: How do you help parents motivate and engage their kids to keep their teeth clean?

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Two pots will help create a barrier between the two different strategies that will keep things clean.

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