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
Which of the following true about ventilation and perfusion in alveoli in erect posture? 
Select and explain. 
A. Ventilation/perfusion ratio is maxm at apex, B. Ventilation/perfusion ratio is maxm at base, C. Ventilation is max at apex, D. Perfusion is max at apex
A: Ventilation/perfusion ratio is maxm at apex
Answer: A: Ventilation/perfusion ratio is maxm at apex 
Explanation: The V/Q ratio can therefore be defined as the ratio of the amount of air reaching the alveoli per minute to the amount of blood reaching the alveoli per minute--a ratio of volumetric flow rates. ... The V/Q ratio can be measured with a ventilation/perfusion scan. A V/Q mismatch can cause a type 1 respiratory failure Ref: guyton and hall textbook of medical physiology 12 edition page number: 320,321,322