This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Physiology
With increase in age which of the following is true for lungs 
Select and explain. 
A. Pulmonary compliance increases, B. Residual volume decreases, C. Mucocillary clearance increases, D. The alveolar dead space decreases
A: Pulmonary compliance increases
Answer: A: Pulmonary compliance increases 
Explanation: Ageing and Lung Changes * Decreased chest wall compliance is counter balanced by a loss of elastic recoil of the lungs (increased lung compliance), which is due to a decrease in the number of parenchymal elastic fibers. * Chest wall and thoracic spine deformities which leads to increase work of breathing. * Dilation of air spaces: "senile emphysema". * Respiratory muscle strength decreases with age and this impairs effective cough, which is impoant for airway clearance. * Clearance of paicles from the lung through the mucociliary elevator is decreased and associated with ciliary dysfunction. * The alveolar dead space increases with age, affecting aerial oxygen without impairing the carbon dioxide elimination. * The airways receptors undergo functional changes with age and are less likely to respond to drugs used in younger counterpas * Decreased sensation of dyspnea and diminished ventilatory response to hypoxia and hypercapnia, making them more vulnerable to ventilatory failure during high demand states (ie, hea failure, pneumonia, etc) * Decreases in the volume of the thoracic cavity and reduced lung volumes. Hence Residual volume increases. Ref:- Relationship between chest wall and pulmonary compliance and age Charles Mittman, Norman H. Edelman, Ahur H. Norris, and Nathan. Pg num:- 202