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
Anterior cardiac veins open into: 
Select and explain. 
A. Right atrium, B. Great cardiac vein, C. Coronary sinus, D. Marginal vein
A: Right atrium
Answer: A: Right atrium 
Explanation: Right atrium