What is a colorless, odorless, and poisonous gas found in cigarette smoke?

The correct answer is carbon monoxide. This gas is colorless, odorless, and highly toxic, making it particularly dangerous. It is produced by the incomplete combustion of carbon-containing substances and is a significant component of cigarette smoke. When inhaled, carbon monoxide binds to hemoglobin in the blood much more effectively than oxygen does, which can lead to reduced oxygen delivery to the body's organs and tissues. This can result in a range of health issues, from impaired brain function to even death in severe cases.

In contrast, carbon dioxide is a natural component of the air and is not poisonous at typical atmospheric levels, although elevated levels can lead to suffocation in enclosed spaces. Nitrogen oxide refers to a group of gases that can contribute to air pollution and respiratory problems but is not primarily recognized as a component of cigarette smoke. Formaldehyde is an organic compound that can be found in tobacco smoke but is more associated with irritant effects and long-term carcinogenic potential rather than a primary poison like carbon monoxide.