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
In the etiology of endometriosis Sampson's theory is : 
Select and explain. 
A. Implantation theory, B. Coelomic metaplasia theory, C. Metastatic theory, D. Histogenesis by induction
A: Implantation theory
Answer: A: Implantation theory 
Explanation: Implantation theory