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
Struma ovaril is composed entirely of ? 
Select and explain. 
A. Mature thyroid tissue, B. Immature thyroid tissue, C. Pimary ovarian carcinoid tissue, D. None of the above
A: Mature thyroid tissue
Answer: A: Mature thyroid tissue 
Explanation: Ans. is 'a' i.e., Mature thyroid tissue