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
Which of the following opens directly into right atrium? 
Select and explain. 
A. Anterior cardiac vein, B. Oblique vein, C. Middle cardiac vein, D. Great cardiac vein
A: Anterior cardiac vein
Answer: A: Anterior cardiac vein 
Explanation: Following opens into right atrium
-        Superior vena cava
-        Inferior vena cava
-        Coronary sinus
-        Venae cordis minimae
-        Anterior cardiac vein
-        Right marginal vein