This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: JIPMER 2019, 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. 100 ml-1, respectively and the O2 consumption is 300 ml-min-1. The Cardiac output in liters min-1 is: 
Select and explain. 
A. 5, B. 8, C. 9, D. 7.5
D: 7.5
Answer: D: 7.5 
Explanation: - Oxygen level in aerial blood is given as 20ml / 100ml of blood. - Oxygen level in venous blood is given as 16ml / 100ml of blood. - O2 consumption = 300 ml / min - for entire blood volume (i.e given in liters)- By Fick's formula,