This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Special Senses, Subject name: Physiology
Which muscle is contracted as pa of the pupillary light reflex? 
Select and explain. 
A. Ciliary muscle, B. Pupillary dilator muscle, C. Pupillary sphincter muscle, D. Radial fibers of the iris
C: Pupillary sphincter muscle
Answer: C: Pupillary sphincter muscle 
Explanation: In a normal individual, shining a light in either eye will result in both pupils constricting due to contraction of the pupillary sphincter muscles. In contrast, the pupillary dilator muscle dilates the pupil. The ciliary muscle is involved in focusing the eye (accommodation).