Air is around us. We can not see it, smell it, or taste it. But we can feel the wind blow. We can see the wind move waves on the water, clouds in the sky, and tree branches. Wind is moving air.
Without air we could not breathe. There could be no living plants or animals. Because sound travels through air, without air there would be silence. The movement of air can support a large, heavy plane.
Air is a mixture of gases and water vapor. The most important gases in the air are nitrogen and oxygen. 78 percent of the air is made up of nitrogen, and about 21 percent of oxygen. Almost all living things use the oxygen in air. Fire cannot burn without oxygen.
2017届江苏省高考英语一轮复习:必修2 Unit 1课时提升作业(牛津译林版)
2017届(全国卷地区)高考英语一轮复习学生手册:必修4 Unit 3《A taste of English humour》作业手册
2017届高考英语一轮复习:书面表达专项训练【5】(含范文)
2017届江苏省高考英语一轮复习:必修1 Unit 1课时提升作业(牛津译林版)
2017届江苏省高考英语一轮复习:必修2 阶段评估检测(牛津译林版)
2017届(全国卷地区)高考英语一轮复习学生手册:必修5 Unit 3《Life in the future》听课手册
2017届江苏省高考英语一轮复习:必修3 阶段评估检测(牛津译林版)
2017届(全国卷地区)高考英语一轮复习学生手册:必修4 Unit 5《Theme parks》作业手册
2017届高考英语一轮复习:书面表达专项训练【4】(含范文)
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2017届江苏省高考英语一轮复习:必修3 Unit 3课时提升作业(牛津译林版)
2017届江苏省高考英语一轮复习:必修2 Unit 2课时提升作业(牛津译林版)
2017届江苏省高考英语一轮复习:必修1 Unit 2课时提升作业(牛津译林版)
2017届(全国卷地区)高考英语一轮复习学生手册:必修4 Unit 2《Working the land》听课手册
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2017届江苏省高考英语一轮复习:必修2 Unit 3梯级演练·强技提能(牛津译林版)
2017届江苏省高考英语一轮复习:必修3 Unit 3梯级演练·强技提能(牛津译林版)
2017届高考英语一轮复习:书面表达专项训练【2】(含范文)
2017届江苏省高考英语一轮复习:必修3 Unit 1课时提升作业(牛津译林版)
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2017届高考英语一轮复习:书面表达专项训练【1】(含范文)
2017届江苏省高考英语一轮复习:必修4 Unit 2课时提升作业(牛津译林版)
2017届江苏省高考英语一轮复习:必修2 Unit 1梯级演练·强技提能(牛津译林版)
2017届江苏省高考英语一轮复习:必修1 Unit 3梯级演练·强技提能(牛津译林版)
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2017届(全国卷地区)高考英语一轮复习学生手册:必修4 Unit 5《Theme parks》听课手册
2017届江苏省高考英语一轮复习:必修4 Unit 2梯级演练·强技提能(牛津译林版)
2017届江苏省高考英语一轮复习:必修2 Unit 2梯级演练·强技提能(牛津译林版)
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2017届高考英语一轮复习:书面表达专项训练【20】(含范文)