This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anatomy
All of the following are true about coronary aery, EXCEPT: 
Select and explain. 
A. Right coronary aery lies in right anterior coronary sulcus, B. Left anterior descending aery is a branch of left coronary aery, C. Usually 3 obtuse marginal aeries arise from left coronary aery, D. In 85% cases posterior descending interventricular aery arises from right coronary aery
C: Usually 3 obtuse marginal aeries arise from left coronary aery
Answer: C: Usually 3 obtuse marginal aeries arise from left coronary aery 
Explanation: Only one obtuse marginal aery(OM1) arise from circumflex branch of left coronary aery. This obtuse marginal branch serve as a boundary between the proximal and distal poion of left circumflex aery(LCx). Poion of left circumflex aery proximal to obtuse marginal aery is called proximal LCx, whereas the segment below OM1 is the distal LCx. Ref: Clinical Anatomy for Medical Students By Richard S snell, 6th Edition, Pages 103-4