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
[{'content': 'What is true about sinus venosus? \nSelect and explain. \nA. Forms rough wall of right atrium, B. Forms smooth wall of right atrium, C. Forms right coronary sinus, D. Forms left leaflet of coronary sinus', 'role': 'user'}, {'content': "Answer: B \nExplanation: Sinus venosus forms smooth posterior pa or sinus venarum of right atrium. BD CHAURASIA'S HUMAN ANATOMY VOLUME1. 6TH EDITION.Page no 255", 'role': 'assistant'}]