This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiac Output, Subject name: Physiology
In a measurement of cardiac output using the Fick principle, the O2 concentrations of mixed venous and aerial blood are 16 and 20 ml/min, respectively and the O2 consumption is 300 ml/min, The cardiac output in liters/ min is: 
Select and explain. 
A. 5, B. 8, C. 9 Type II Coical interstitial cells, D. 7.5
D: 7.5
Answer: D: 7.5 
Explanation: Fick's principle for measuring cardiac output - Given values are - O2 consumption - 300 ml / min Aerial O2 - 20 ml Venous O2 - 16 ml 7.5 Lt / min