Which of the following is NOT a greenhouse gas?

Monoxide, specifically carbon monoxide, does not qualify as a greenhouse gas. Greenhouse gases are defined by their ability to trap heat in the Earth’s atmosphere and contribute to the greenhouse effect, which maintains the planet's temperature. Carbon dioxide, methane, and nitrous oxide are all well-known greenhouse gases; they effectively absorb and emit infrared radiation, leading to warming of the atmosphere.

Carbon monoxide, while it can affect air quality and has implications for health and environmental conditions, does not significantly contribute to the greenhouse effect. Its role is more associated with air pollution rather than climate change. Understanding the distinction between greenhouse gases and other atmospheric gases is essential in comprehending how various substances impact the environment.