The correct answer is tobacco.
An agent that exhibits the tendency to modify the genetic material of a species, thereby resulting in mutation is known as a mutagen. Tobacco is a chemical mutagen. Tobacco smoke comprises a mixture of many chemicals that incorporates about 60 carcinogens, that is, the chemicals that can result in cancer.
One of the examples is benzopyrene found in tobacco smoke, which has been found to result in mutations. Therefore, tobacco is regarded as a chemical mutagen.