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
Adenomyosis is ? 
Select and explain. 
A. Hyperplasia of glands in the endometricum, B. Metaplasia of endometrial glands, C. Presence of endometrial tissue within the myometrium, D. Presence of myometrial tissue within the endometrium
C: Presence of endometrial tissue within the myometrium
Answer: C: Presence of endometrial tissue within the myometrium 
Explanation: Adenomysis is the presence of endometrial tissue within the myometrium of uterus.