This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thorax, Subject name: Anatomy
Direct opening in the right atrium with 
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: All veins of hea except the anterior cardiac veins and the venae cordis minimi drain into the coronary sinus which opens into the right atrium.The anterior cardiac veins and the venae cordis minimi open directly into the right atrium. BD CHAURASIA'S HUMAN ANATOMY .VOLUME 1.FIFTH EDITION.Page no-254