This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Heart, Circulation, and Blood, Subject name: Physiology
For doing ABG, which of the following is used? 
Select and explain. 
A. Whole blood, B. Plasma, C. RBC, D. Serum
A: Whole blood
Answer: A: Whole blood 
Explanation: Ans: a: (Whole blood)Whole arterial blood is taken for ABG.