This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Social & Preventive Medicine
Other than nitrogen and oxygen, which one of the following is the next most abundant gas in the dry air of lower atmosphere ? 
Select and explain. 
A. Argon, B. Carbon dioxide, C. Helium, D. Hydrogen
B: Carbon dioxide
Answer: B: Carbon dioxide 
Explanation: None