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You can ask some people to join the voluntary program in which they’ll _______ trash from the river.

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If I have time, I _______ some trees in my neighborhood.

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We should take a bus often _______ we can help reduce air pollution in the city.

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A lot of people _______ trash into rivers and make the water polluted.

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The scientists will explain some techniques on how to _______ household things.

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Governments worldwide (A) are working (B) together to protect (C) the environment for (D) pollution.

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Burning coal to produce electricity _______ the air.

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It is (A) too (B) hot today – please turn on (C) the air condition (D).