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Public bicycle appeard is good or bad
With the development and innovation of science and technology, the Inter...
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Fire safetyFire is a two-edged sword. I searched on the Internet. I fond that in 20...
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Bicycle's historyDo you know that the first bicycle in the world did not have pedals? On...
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Air pollutionNowadays, air pollution becomes a major topic in the society. PM 2.5 is ...
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Environmental pollution
Did you know that many animals,plants,and forests on earth are disapp...
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