The correct answer is: A. Pupil.
The pupil is the black hole in the center of the iris. It controls the amount of light that enters the eye by contracting and dilating. When it is dark, the pupil dilates to let in more light. When it is bright, the pupil contracts to let in less light.
The iris is the colored part of the eye. It is made up of muscles that control the size of the pupil.
The cornea is the clear front part of the eye. It helps to focus light on the retina.
The retina is the light-sensitive tissue at the back of the eye. It converts light into electrical signals that are sent to the brain. The brain interprets these signals as images.