Air
空气
You can't see it. You can't touch it. But you can't live without it. What is it? It is air.
Air is very important. It is all around us when we walk and play. It is all around us when we sit down or sleep. We live in air.
All living things need air. We can live without food or water for a few days, but we cannot live without air for even a few minutes. When we are working or running, we need more air. When we are asleep, we need less air.
注释：
1）You can't live without it. 没有它你就不能生存。
2）We live in air. 我们生活在空气中。
3）All living things need air. 一切有生命的东西都需要空气。
4）We cannot live without air for even a few minutes. 没有空气，即便是几分钟我们也活不了。
Air is a precious resource that is often taken for granted. It is invisible, yet it is the very essence of life. Without air, life as we know it would cease to exist. The importance of air cannot be overstated, and it is crucial that we take steps to protect it.
Firstly, air is vital for human health. It provides the oxygen that our bodies need to function. Without a sufficient supply of clean air, we are at risk of developing respiratory diseases and other health problems. This is why it is important to maintain air quality standards and to reduce pollution.
Secondly, air plays a critical role in the ecosystem. It is the medium through which plants carry out photosynthesis, a process that is essential for the production of oxygen and the removal of carbon dioxide. This balance is crucial for the survival of all living organisms.
Lastly, the protection of air quality is not just a local issue, but a global one. The effects of air pollution can travel across borders, affecting countries and regions far from the source of the pollution. This is why international cooperation is necessary to address this issue.
In conclusion, air is an invaluable resource that we must protect. By taking steps to reduce pollution and maintain air quality, we can ensure a healthier future for ourselves and for the planet.
空气，这个我们赖以生存的无形之物，常常被我们所忽视。尽管它看不见摸不着，却是我们生命的基础。没有空气，我们所熟悉的生命形式将不复存在。空气的重要性不容小觑，我们必须采取行动来保护它。
首先，空气对我们的健康至关重要。它为我们提供了必不可少的氧气，没有足够的清洁空气，我们可能会遭受呼吸系统疾病和其他健康问题的困扰。因此，维护空气质量标准和减少污染是至关重要的。
其次，空气在生态系统中扮演着核心角色。它是植物进行光合作用的媒介，这个过程对于产生氧气和吸收二氧化碳至关重要。这种平衡对于所有生物的生存都是至关重要的。
最后，保护空气质量不仅是一个地方性问题，它是一个全球性的问题。空气污染的影响可以跨越国界，影响远离污染源的国家和地区。因此，需要国际间的合作来共同解决这个问题。
总之，空气是我们必须珍视的宝贵资源。通过减少污染和维护空气质量，我们可以为自己和地球创造一个更健康的未来。
Air is a mixture of gases that surrounds the Earth and is essential for the survival of all living organisms. The composition of air is primarily nitrogen (about 78%), followed by oxygen (about 20.9%), with trace amounts of other gases such as argon, carbon dioxide, and water vapor.
Oxygen, which makes up about one-fifth of the air, is critical for respiration in animals and humans. It is also necessary for combustion, which is the process of burning that releases energy.
Nitrogen, which is about four-fifths of the air, plays a less visible but equally important role. It is a key component in the production of proteins and other essential biological molecules. Additionally, nitrogen is used in the manufacture of fertilizers, which are crucial for agriculture.
Carbon dioxide, while present in much smaller amounts, is vital for the process of photosynthesis in plants. This process converts carbon dioxide and water into glucose and oxygen, providing food for the plant and replenishing the oxygen in the air.
Air also contains other gases that have various uses and effects. For example, argon is used in lighting and is known for its inert properties, while water vapor contributes to the Earth's weather patterns and climate.
Understanding the composition and importance of air is fundamental to appreciating the complex systems that support life on Earth.
空气，这个我们每天都在呼吸的无形之物，对地球上所有生物的生存至关重要。空气主要由氮气（大约占78%）组成，其次是氧气（大约占20.9%），还有少量的其他气体，如氩、二氧化碳和水蒸气。
氧气，这个我们呼吸的气体，占空气的五分之一，对动物和人类的呼吸至关重要。它也是燃烧过程（释放能量的燃烧过程）的必要条件。
氮气，这个我们呼吸的气体，占空气的五分之四，虽然不那么明显，但同样重要。它是生产蛋白质和其他必需生物分子的关键成分。此外，氮气还用于制造肥料，这对农业至关重要。
二氧化碳，尽管在空气中含量较少，但对植物的光合作用过程至关重要。这个过程将二氧化碳和水转化为葡萄糖和氧气，为植物提供食物并补充空气中的氧气。
空气还含有其他具有各种用途和影响的气体。例如，氩用于照明，以其惰性特性而闻名，而水蒸气则有助于地球的天气模式和气候。
了解空气的组成和重要性是欣赏和支持地球上生命复杂系统的基础。