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
Intrapulmonary shunting refers to 
Select and explain. 
A. Anatomical dead space, B. Alveolar dead space, C. Wasted ventilation, D. Perfusion in excess of ventilation
D: Perfusion in excess of ventilation
Answer: D: Perfusion in excess of ventilation 
Explanation: A pulmonary shunt often occurs when the alveoli fill with fluid, causing pas of the lung to be unventilated although they are still perfused. Intrapulmonary shunting is the main cause of hypoxemia (inadequate blood oxygen) in pulmonary edema and conditions such as pneumonia in which the lungs become consolidated Ref: guyton and hall textbook of medical physiology 12 edition page number:333,334,335