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
[{'content': "Which of the following duct commences in the abdomen as an elongated lymph sac of the cisterna chyli \nSelect and explain. \nA. Thoracic duct, B. Gartner's duct, C. Bile duct, D. Hepatic duct", 'role': 'user'}, {'content': 'Answer: A \nExplanation: At the upper end of cysterna chyli, thoracic duct begins.', 'role': 'assistant'}]