Pupillary Light Reflex Mechanism Steps:

• Bright light hits retina, sending signals via optic nerve to pretectal nucleus.
• Signals activate parasympathetic pathway through oculomotor nerve.
• Parasympathetic stimulation contracts circular (sphincter) pupillary muscle.
• Sympathetic inhibition relaxes radial (dilator) pupillary muscle.
• Combined actions constrict pupil, reducing light entry.

Why C is correct:

• Pupil constriction (miosis) requires circular muscle contraction to narrow the pupil and radial muscle relaxation to prevent dilation, per autonomic innervation of iris muscles.

Why the others are wrong:

• A: Ciliary muscle contraction adjusts lens for accommodation, not pupil size.
• B: Suspensory ligaments tighten for lens focusing, unrelated to light reflex.
• D: Suspensory ligaments are not involved in pupillary response.

Final answer: C