The atmosphere acts in several ways to support life on the Earth. One of these is that it protects the planet from detrimental radiation emitted by the sun. In addition, the atmosphere provides life-giving oxygen for animals and carbon dioxide for plants. The atmosphere may appear simple, but it is actually complex and has distinct layers. These layers are divided based upon their height above sea level. There are five major layers of the atmosphere. They are the troposphere, stratosphere, mesosphere, thermosphere, and exosphere. The troposphere is the layer of the atmosphere closest to the Earth's surface. It extends from the ground to approximately seventeen kilometers above sea level at its highest point. This layer contains the greatest mass of the atmosphere around seventy-five to eighty percent. It is also the warmest layer and has most of the weather that people experience. The stratosphere extends from the troposphere to around fifty kilometers above sea level. It contains most of the rest of the atmosphere in addition to the ozone layer. This is the region that keeps the Earth safe from much of the sun's radiation. Temperatures are very cold at the lower part of the stratosphere but become warmer higher up due to the absorption of radiation. The next three layers are found high above the planet's surface. The first is the mesosphere, which extends from the stratosphere to around eighty-five kilometers above sea level. This is the region where most meteors are incinerated as they hit the atmosphere. Temperatures drop once again in this layer. They may decline to more than minus 100 degrees Celsius. The fourth layer is the thermosphere. It extends alt the way up to 690 kilometers above sea level. It is where the aurora borealis, or northern lights, form. In addition, most spacecraft and space stations orbit the planet there. Temperatures in the thermosphere vary from extremely cold to extremely hot. Last is the exosphere. It extends thousands of kilometers above the ground until there is no longer an atmosphere but only outer space. Instead, there are simply random molecules of hydrogen and helium. 1. Based on the passage, what is probably true about the Earth's atmosphere? A. It has more mass than the planet itself. B. Humans still have a great deal to learn about it. C. Life on the planet could not exist without it. D. It formed over the course of billions of years. 2. Which of the following is true regarding the troposphere? A. It is the largest in area of all the layers of the atmosphere. B. It constantly changes due to the effects of weather. C. It covers the area upon which plants and animals live. D. It contains high amounts of both nitrogen and oxygen. 3. Where are the aurora borealis found? A. In the exosphere B. In thẻ thermosphere C. In the stratosphere D. In the mesosphere 4. Which of the following statements does paragraph 4 support? A. Spacecraft and space stations orbit from the exosphere. B. The mesosphere is further from the ground than the thermosphere. C. The exosphere extends to the boundaries of outer space. D. The temperature may reach 100 degrees Celsius in the mesosphere. TÌM DẪN CHỨNG