Answer the following question given this paragraph: A: You can tell that they are different compounds from their very different properties. Carbon dioxide is a harmless gas that living things add to the atmosphere during respiration. Carbon monoxide is a deadly gas that can quickly kill people if it becomes too concentrated in the air. Q: What type of gas is a harmless gas that living things add to the atmosphere during respiration? Choices: - helium - oxygen - Hydrogen - carbon dioxide A:
A:
carbon dioxide