The _______________ regulates and controls the amount of light entering the eye.

Correct option is D

The iris regulates and controls the amount of light entering the eye.

Explanation:
● The iris is the colored part of the eye surrounding the pupil.
● It contains muscles that contract or dilate the pupil, adjusting the amount of light entering the eye based on the surrounding brightness.
● In bright light, the pupil contracts (a process called miosis) to reduce the amount of light.
● In dim light, the pupil dilates (a process called mydriasis) to allow more light to enter.

Information Booster:
● The pupil is the opening through which light enters the eye, and its size is controlled by the iris.
● The retina converts light into electrical signals that are transmitted to the brain for visual perception.
● The cornea helps focus light onto the retina but does not regulate its entry.
● Proper functioning of the iris is crucial for protecting the retina from excessive light and for adapting vision to different lighting conditions.

Additional Information:

• (A) Pupil: The opening, but it is regulated by the iris.
• (B) Retina: Processes light into signals, unrelated to light regulation.
• (C) Cornea: Focuses light onto the retina but does not control light entry.