What is nitrogen dioxide (NO2)?

Nitrogen dioxide (NO2) is indeed classified as an extremely poisonous gas, which makes option B the correct choice. As a significant air pollutant, it is a reddish-brown gas with a characteristic sharp, acrid odor. It is a product of combustion processes, such as those that occur in vehicles and industrial operations, and is known for its harmful effects on human health and the environment. Exposure to high levels of nitrogen dioxide can lead to respiratory problems and other health issues.

While nitrogen dioxide is a component of the atmosphere and contributes to the formation of smog and acid rain, its toxicity is the prime reason for its classification as a hazardous gas. Thus, simply labeling it as a gaseous component of the atmosphere does not capture its environmental and health risks, nor does it reflect its severe impact on air quality and public health. Understanding the nature of nitrogen dioxide and its effects is crucial, especially in discussions surrounding air pollution and public safety.