This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endometriosis, Subject name: Gynaecology & Obstetrics
[{'content': 'Pain in endometriosis correlates with: \nSelect and explain. \nA. Depth of invasion, B. Multiple sites, C. CA 125, D. Stage of disease', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. is a, i.e. Depth of invasionRef: Leon Speroff, 8/ed, pl230-1231"The intensity of pain associated with deeply infiltrating endometriosis relates to the depth of penetration and to the proximity or direct invasion of nerves". - Ref: Leon Speroff, 8th/ed, pl230"However there is no relationship between stage, site or the morphological characteristic of pelvic endometriosis and pain". - Ref: Leon Speroff, 8th/ed, pi231', 'role': 'assistant'}]