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
The gradient of alveolar aerial oxygen tension increases in A/E: 
Select and explain. 
A. Diffusion defect, B. Right - Left shunt, C. Hypoventilation, D. Ventilation perfusion abnormality
C: Hypoventilation
Answer: C: Hypoventilation 
Explanation: C i.e Hypoventilation