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: Pathology
The commonest site of endometriosis 
Select and explain. 
A. Vagina, B. Ovary, C. Urinary bladder, D. Peritoneal cavity
B: Ovary
Answer: B: Ovary 
Explanation: Endometriosis

Endometriosis (ectopic endometrium) is the term used to describe the presence of endometrium (endometrial glands or stroma) in abnormal locations outside the uterus.
It occurs in following sites, in decreasing order of frequency -

1. Ovary                       2. Uterine ligaments           3. Rectovaginal septum                     4. Pelvic peritoneum
5. Laprotomy scar       6. Umbilicus, vagina, vulva or appendix.

Adenomyosis is the presence of endometrial tissue in the uterine wall, i.e., in the myometrium.