This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Abdomen and pelvis, Subject name: Anatomy
Which of the following is the anterior relation to first pa of duodenum ? 
Select and explain. 
A. root of mesentary, B. superior mesenteric vessels, C. transverse mesocolon, D. gallbladder
D: gallbladder
Answer: D: gallbladder 
Explanation: Visceral Relations of 1st pa of duodenum Anteriorly: 1)Quadrate lobe of liver, and 2) gall bladder. Ref : B D Chaurasia's Human Anatomy , seventh edition , voulme 2 , pg. no., 286 ( Fig. 20.8a )