This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Environment and health, Subject name: Social & Preventive Medicine
[{'content': 'Which one of the following is not a greenhouse gas? \nSelect and explain. \nA. Carbon monoxide, B. Methane, C. Nitrous oxide, D. Water vapour', 'role': 'user'}, {'content': "Answer: A \nExplanation: Green house gases Water vapour (Highest contribution) Carbon dioxide (second highest contribution) Methane Ozone: Ozone later is beneficial as it cuts down IV transmission CFC's depletes ozone layer Ref : Wikipedia", 'role': 'assistant'}]