Question

what is a colorless, odorless, and poisonous gas found in cigarette smoke?
carbon monoxide
nitrogen oxide
carbon dioxide
magnesium oxide

Explanation:

Carbon monoxide is a colorless, odorless, and poisonous gas. It is produced during incomplete combustion, such as in cigarette smoke. Magnesium oxide is a solid. Carbon dioxide is a colorless and odorless gas but is not poisonous in the context of being a harmful component in cigarette smoke like carbon monoxide. Nitrogen oxide has a distinct odor in some forms and is not the gas described here.

Answer:

Carbon monoxide