The correct answer is A. Iodine.
Iodine is a non-metallic, lustrous, deep purple-black solid at standard temperature and pressure. It is the heaviest stable halogen and exists as a diatomic molecule. The element has one of the highest atomic numbers of any naturally occurring non-metal.
Iodine is a member of the halogen group and is chemically similar to chlorine and bromine. It is a highly reactive element and is used in a variety of applications, including photography, medicine, and industry.
Iodine is a greenish yellow gas with a characteristic odor at room temperature. It is soluble in water and alcohol.
Chlorine is a pale yellow-green gas at standard temperature and pressure. It is an extremely reactive element and is used in a variety of applications, including bleaching, disinfection, and production of plastics.
Carbon monoxide is a colorless, odorless gas that is highly toxic. It is produced by incomplete combustion of carbon-containing materials.
Hydrogen sulfide is a colorless, flammable gas with a rotten egg odor. It is produced by the decomposition of organic matter.
Iodine is the only option that is a greenish yellow gas with a characteristic odor at room temperature.