Which one of the following is not a greenhouse gas ?
**Core Concept**
Carbon dioxide, methane, and nitrous oxide are well-known greenhouse gases that contribute to global warming and climate change. These gases trap heat in the atmosphere, leading to a rise in Earth's temperature.
**Why the Correct Answer is Right**
The correct answer is not listed among the options. However, I can provide explanations for each option to clarify why they are incorrect. Carbon dioxide (CO2) is a major greenhouse gas released through fossil fuel combustion, deforestation, and land-use changes. Methane (CH4) is a potent greenhouse gas emitted from agriculture, natural gas systems, and landfills. Nitrous oxide (N2O) is a long-lived greenhouse gas produced by agricultural activities, industrial processes, and burning fossil fuels.
**Why Each Wrong Option is Incorrect**
**Option A:** Carbon dioxide is a well-established greenhouse gas, so this option is incorrect.
**Option B:** Methane is a potent greenhouse gas, making this option incorrect.
**Option C:** Nitrous oxide is a long-lived greenhouse gas, so this option is also incorrect.
**Clinical Pearl / High-Yield Fact**
The Kyoto Protocol, an international treaty, aimed to reduce greenhouse gas emissions by developed countries. This treaty was signed in 1997 and came into effect in 2005.
**Correct Answer:** D.