Final answer:
Carbon dioxide (CO₂) is the greenhouse gas most responsible for the observed global warming trends due to its high concentration and long-lasting effect in the Earth's atmosphere. the correct option is (a).
Step-by-step explanation:
While multiple greenhouse gases contribute to global warming, carbon dioxide (CO₂) is the primary driver. Human activities, such as the burning of fossil fuels (coal, oil, and natural gas), deforestation, and industrial processes, release substantial amounts of CO₂ into the atmosphere. This increased concentration of carbon dioxide enhances the greenhouse effect, trapping more heat and leading to a rise in global temperatures.
Methane (CH₄) and nitrous oxide (N₂O) are also significant contributors to the greenhouse effect, but they have a shorter atmospheric lifetime compared to carbon dioxide. Water vapor (H₂O) is a natural component of the Earth's atmosphere and plays a crucial role in the greenhouse effect, but its concentration is primarily controlled by natural processes.
Methane (CH₄) and nitrous oxide (N₂O) are also potent greenhouse gases, but their levels and impact are less than that of CO₂. The answer to the question is A. Carbon dioxide (CO₂).