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
The blockage of blood flow in the proximal pa of the anterior interventricular aery could deprive a large area of hea tissue of blood supply, unless a substantial retrograde flow into this aery develops an impoant anastomosis with which other aery? 
Select and explain. 
A. Circumflex, B. Left marginal, C. Posterior interventricular, D. Right coronary
C: Posterior interventricular
Answer: C: Posterior interventricular 
Explanation: The anterior interventricular aery and posterior interventricular aery travel on the anterior and posterior surfaces of the interventricular groove. These two vessels often anastamose. If there was a very extensive anastomoses between the anterior and posterior interventricular aeries, it is possible that the posterior interventricular aery might supply the tissue usually fed by the anterior interventricular aery. The other aeries listed would not be able to anastamose with anterior interventricular aery; they supply other areas of the hea. Ref: Seward J.B., Malouf J.F., Edwards W.D., Tajik A. (2011). Chapter 4. Functional Anatomy of the Hea. In V. Fuster, R.A. Walsh, R.A. Harrington (Eds), Hurst's The Hea, 13e.