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: Anatomy
All of the following are mesodermal in origin except - 
Select and explain. 
A. Dilators of iris, B. Iris stroma, C. Ciliary body, D. Choroid
A: Dilators of iris
Answer: A: Dilators of iris 
Explanation: None