This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Surgery
Most common and best gas for laparoscopy: 
Select and explain. 
A. CO2, B. N2, C. Air, D. O2
A: CO2
Answer: A: CO2 
Explanation: Ans: a (CO2) Ref:Bailey, 24th ed,p. 107CO is the gas used to create pneumoperitoneumMethods for creating pneumoperitoneum-Open- more cumbersome, but more efficientClosed- blind puncture"It was desirable that intraabdominal pressure should be between 12-14 mm Hg and should never be allowed to exceed 20 mm Hg.- (Ajay Yadav, p. 168).