Pupillary response to sudden light dimming

Steps:

• Pupils constrict in bright light to reduce light entry and dilate in dim light to increase it.
• Graph likely shows initial constriction followed by sudden dilation around 20-30 seconds.
• Dilation indicates decreased light intensity, as the reflex adjusts pupil size inversely to brightness.
• Sudden change in pupil size matches abrupt light alteration, not gradual.

Why C is correct:

• Pupil dilates rapidly when light suddenly dims, per the pupillary light reflex, which widens the pupil to gather more light (inverse relationship with intensity).

Why the others are wrong:

• A: Slow brightening causes gradual constriction, not sudden dilation.
• B: Sudden brightening triggers immediate constriction, shrinking the pupil.
• D: Slow dimming leads to gradual dilation, not a sharp pupil size increase.

Final answer: C