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: Ophthalmology
Iris is thinnest at: 
Select and explain. 
A. Ciliary zone, B. pupil margin, C. Base, D. Collarette
C: Base
Answer: C: Base 
Explanation: The iris is thinnest at its attachment to the ciliary body (base) so that if it tends to give way in this region.