This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Head and neck, Subject name: Anatomy
[{'content': 'Superior vena cava is formed by? \nSelect and explain. \nA. Vitelline veins, B. Supracardinal vein, C. Infracardinal vein, D. Common cardinal vein', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Developmentally, the superior vena cava consists of two pas: first and second. The first pa develops from the right anterior cardinal vein caudal to oblique transverse anastomosis. The second pa develops from the right common cardinal vein. Reference: Textbook of clinical embryology, Vishram Singh,1st edition, page no.223-224', 'role': 'assistant'}]