The correct answer is: A. Carbon dioxide.
Carbon dioxide is the most abundant greenhouse gas in Earth’s atmosphere. It is produced by the burning of fossil fuels, such as coal, oil, and natural gas, as well as by the decomposition of organic matter. Carbon dioxide is also released into the atmosphere when forests are cleared.
Human activities are increasing the amount of carbon dioxide in the atmosphere at an alarming rate. This is causing the Earth’s temperature to rise, which is leading to a number of negative effects, such as more extreme weather events, rising sea levels, and changes in plant and animal life.
HFCs, ozone, and water vapor are also greenhouse gases, but they are not as abundant as carbon dioxide. HFCs are man-made chemicals that are used in refrigerants and air conditioners. Ozone is a gas that is found in the stratosphere, which is the layer of the atmosphere that protects us from the sun’s harmful ultraviolet rays. Water vapor is a gas that is found in the atmosphere and is a natural greenhouse gas.
However, carbon dioxide is the most important greenhouse gas because it is the most abundant and it has the greatest impact on the Earth’s climate.