Question

what structure regulates the amount of light passing to the visual receptors of the eye?
iris
aqueous humor
cornea
lens

Explanation:

To solve this, we analyze each option:

• Iris: Controls the size of the pupil, regulating light entering the eye (pupil is the opening through which light passes to receptors).
• Aqueous humor: Maintains eye pressure and nourishes, not light regulation.
• Cornea: Refracts light, not regulate light amount.
• Lens: Focuses light, not regulate light quantity.

So the iris is the correct structure.

Answer:

A. iris