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: Radiology
[{'content': "Point B in treatment of Ca Cervix by radiotherapy corresponds to - \nSelect and explain. \nA. Obturator nodes, B. Machenrodt's ligament, C. Ischial tuberosity, D. Round ligament", 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]