1 . Trees ________ oxygen and ________ carbon dioxide.
A.give off, let off | B.release, give on |
C.let out, absorb | D.absorb, let out |
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2 . I’d like to stand on the top of the mountain and take in some fresh air.
A.make | B.absorb | C.stop | D.put |
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3 . 树木从空气中吸收有害气体,然后产生氧气供我们呼吸。
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