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Have you ever ________ (be) to the Great Wall?

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________ pollution is necessary. (control)

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An oil leak in the sea caused concerns over ________ pollution. (environment)

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The Earth gets more ________ every day. (pollute)

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Do you do ________ on Earth Day ? (something)

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Susan picked ________ (they) up.

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We have ________ pollution. (control)

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________ a tree is fun. (plant)

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Let's ________ up the garbage. (pick)

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I have never ________ (meet) such a strange person.