Concept:Carbon (IV) oxide is released into the atmosphere during respiration or complete breakdown of organic compounds.Explanation:Plants build-up of organic compounds uses carbon (IV) oxide, not adds it.Absorption of mineral salts does not release carbon (IV) oxide.Thunderstorms do not add carbon (IV) oxide to the atmosphere.When sugars are completely broken down in animals, carbon (IV) oxide is produced and released.Answer:C. sugars are completely broken down in animals