This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bronchopulmonary Segments, Embryonic veins, 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 is a paired structure but shifts towards right associating only with the right atrium as the embryonic hea develops. The left poion shrinks in size and eventually forms the coronary sinus and oblique vein of the left atrium, whereas the right pa becomes incorporated into the right atrium to form the sinus venarum (smooth pa of right atrium).', 'role': 'assistant'}]