The correct answer is: A. ionosphere
The ionosphere is a region of Earth’s atmosphere that is ionized by solar radiation. It is located above the stratosphere and extends from about 50 to 1,000 kilometers (31 to 620 miles) above the Earth’s surface. The ionosphere is important for radio communications because it reflects radio waves back to Earth.
The temperature of the ionosphere increases with altitude. This is because the solar radiation that ionizes the atmosphere also heats it. The highest temperatures in the ionosphere are found in the thermosphere, which is the outermost layer of the ionosphere. The thermosphere extends from about 80 to 600 kilometers (50 to 370 miles) above the Earth’s surface.
The other options are incorrect because they are not regions of Earth’s atmosphere where the temperature increases rapidly. The troposphere is the lowest layer of Earth’s atmosphere. It extends from the Earth’s surface to about 12 kilometers (7.5 miles) above sea level. The temperature of the troposphere decreases with altitude. This is because the air in the troposphere is heated by the Earth’s surface. The stratosphere is the second layer of Earth’s atmosphere. It extends from about 12 to 50 kilometers (7.5 to 31 miles) above sea level. The temperature of the stratosphere increases with altitude. This is because the ozone layer in the stratosphere absorbs ultraviolet radiation from the Sun. The exosphere is the outermost layer of Earth’s atmosphere. It extends from about 500 to 10,000 kilometers (310 to 6,200 miles) above sea level. The temperature of the exosphere decreases with altitude. This is because the air in the exosphere is very thin and there is not enough matter to absorb heat from the Sun.