The correct option is **B. CO\(_{2}\)**. ### Detailed Explanation: 1. **Understanding Global Warming**: - Global warming refers to the long-term increase in Earth's average surface temperature due to human activities, primarily the release of greenhouse gases (GHGs) into the atmosphere. These gases trap heat from the sun, preventing it from escaping back into space, which leads to a warming effect. 2. **Role of Carbon Dioxide (CO\(_{2}\))**: - Carbon dioxide is one of the most significant greenhouse gases. It is produced by various natural processes, such as respiration and volcanic eruptions, but the primary concern is the anthropogenic (human-caused) emissions from burning fossil fuels (like coal, oil, and natural gas) and deforestation. - CO\(_{2}\) has a long atmospheric lifetime, meaning it can remain in the atmosphere for hundreds to thousands of years, contributing to the greenhouse effect over a prolonged period. 3. **Mechanism of Greenhouse Gases**: - Greenhouse gases, including CO\(_{2}\), absorb infrared radiation emitted from the Earth's surface. This absorption and re-emission of radiation lead to an increase in the temperature of the atmosphere, which is the essence of the greenhouse effect. ### Why Other Options Are Incorrect: - **A. O\(_{2}\) (Oxygen)**: - Oxygen is essential for life and is involved in combustion and respiration. However, it does not have significant greenhouse properties. It does not absorb infrared radiation effectively, so it does not contribute to the greenhouse effect or global warming. - **C. N\(_{2}\) (Nitrogen)**: - Nitrogen makes up about 78% of the Earth's atmosphere and is inert, meaning it does not react easily with other substances. Like oxygen, nitrogen does not absorb infrared radiation and therefore does not contribute to global warming. - **D. He (Helium)**: - Helium is a noble gas that is chemically inert and does not participate in any reactions that would lead to greenhouse gas effects. It is not a greenhouse gas and has no role in global warming. ### Summary of Key Points: - **Global warming** is primarily caused by greenhouse gases that trap heat in the atmosphere. - **CO\(_{2\)** is a major greenhouse gas due to its long atmospheric lifetime and ability to absorb infrared radiation. - **O\(_2\)**, **N\(_2\)**, and **He** do not contribute to global warming as they do not have significant greenhouse properties. ### Revision Summary: - The primary gas causing global warming is **CO\(_{2}\)**. - Greenhouse gases trap heat in the atmosphere, leading to increased global temperatures. - Other gases like **O\(_2\)**, **N\(_2\)**, and **He** do not contribute to the greenhouse effect. - Understanding the role of different gases is crucial for addressing climate change and global warming.