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
The severity of pelvic pain in endometriosis correlates best with : 
Select and explain. 
A. Number of implants, B. Depth of invasion, C. Stage of disease, D. Ca 125 levels
B: Depth of invasion
Answer: B: Depth of invasion 
Explanation: Depth of invasion