Two of the major greenhouse gases are carbon dioxide (CO₂) and methane (CH₄). These gases are significant contributors to the greenhouse effect, which traps heat in the Earth's atmosphere and leads to global warming.
Let's review the options:
- Option A: CO₂ and CH₄
- Carbon dioxide (CO₂) is a well-known greenhouse gas released through natural processes like respiration and volcanic eruptions, as well as human activities such as deforestation and burning fossil fuels.
- Methane (CH₄) is another potent greenhouse gas released during the production and transport of coal, oil, and natural gas, as well as from livestock and other agricultural practices.
- Option B: CH₂O and CO
- Formaldehyde (CH₂O) is primarily a pollutant and not a major greenhouse gas.
- Carbon monoxide (CO) is also primarily a pollutant and not a significant greenhouse gas.
- Option C: NO and NO₂
- Nitric oxide (NO) and nitrogen dioxide (NO₂) are primarily air pollutants, contributing to smog and acid rain, but they are not categorized among the major greenhouse gases.
- Option D: O₂ and H₂O
- Oxygen (O₂) is essential for life but is not a greenhouse gas.
- Water vapor (H₂O) is a greenhouse gas, but it is primarily a feedback to the climate rather than a direct driver of climate change.
Considering this information, we determine that the correct answer is:
- Option A: CO₂ and CH₄
Thus, the answer is:
A. CO₂ and CH₄
