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阅读短文，选择正确的答案。 We know the air is very important for us. Without air, we couldn't live. Other creatures can't live either. We need clean air. The dirty air is bad for us. Now the air pollution is very serious in some places. For example, the smoke from some factories make the air dirty. Exhaust gas from cars make the air dirty. The forest fire can make the air dirty, too. So we need to pay attention to the air pollution. We can plant more trees and think of other ways to sovle the problem.
