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: Physiology
Effo during normal respiration is done due to ? 
Select and explain. 
A. Lung elasticity, B. Respiratory air passages, C. Alveolar air spaces, D. Creating negative pleural pressure
A: Lung elasticity
Answer: A: Lung elasticity 
Explanation: A i.e. Lung elasticity