Concept:Greenhouse gases trap heat in the atmosphere, keeping Earth warm. Carbon dioxide is the most important greenhouse gas.Explanation:Greenhouse gases allow sunlight to reach Earth but stop some heat from escaping into space. This trapped heat warms the planet. Carbon dioxide (COâ‚‚) is the main gas responsible for the greenhouse effect. Human activities like burning fossil fuels and deforestation release large amounts of COâ‚‚. Other greenhouse gases include methane and nitrous oxide. However, COâ‚‚ is called the primary greenhouse gas because it stays in the atmosphere for a long time and has the biggest impact on climate change. Oxygen, nitrogen, and argon do not trap heat effectively. Therefore, carbon dioxide is the correct answer.Answer:C. Carbon Dioxide