题目内容
We should keep the earth _________ and stop _________ it.
A.clean; polluting B.to clean; polluting C.clean; to pollute D.to clean; to pollute
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题目内容
We should keep the earth _________ and stop _________ it.
A.clean; polluting B.to clean; polluting C.clean; to pollute D.to clean; to pollute