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: Gynaecology & Obstetrics
[{'content': 'The severity of pelvic pain in endometriosis correlates best with : \nSelect and explain. \nA. Number of implants, B. Depth of invasion, C. Stage of disease, D. Ca 125 levels', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Depth of invasion', 'role': 'assistant'}]