In what chemical form is carbon most commonly found in Earth's atmosphere?

• A. As carbon dioxide (CO_2)
• B. As carbon monoxide (CO)
• C. As methane (CH_4)
• D. As elemental carbon (C)

Answer: (A)

Verified step by step guidance

1. Understand that the question asks about the most common chemical form of carbon in Earth's atmosphere, which means identifying the predominant carbon-containing molecule present in the air around us.
2. Recall that Earth's atmosphere contains various gases, and carbon can exist in different forms such as carbon dioxide (CO\_2), carbon monoxide (CO), methane (CH\_4), or elemental carbon (C).
3. Consider the natural processes that release carbon into the atmosphere, such as respiration, combustion, and volcanic activity, which primarily produce carbon dioxide (CO\_2).
4. Recognize that carbon dioxide (CO\_2) is a stable, abundant gas that plays a key role in the carbon cycle and is present in much higher concentrations than carbon monoxide (CO), methane (CH\_4), or elemental carbon (C) in the atmosphere.
5. Conclude that the most common chemical form of carbon in Earth's atmosphere is carbon dioxide (CO\_2).