**Explanation:**

The combination responsible for admitting different amounts of light into the eye is the **iris and pupil**.

**Iris:**
The iris is the colored part of the eye that surrounds the pupil. It consists of a thin circular muscle called the sphincter muscle and a radial muscle that expands and contracts to control the size of the pupil. The iris controls the amount of light entering the eye by adjusting the size of the pupil.

**Pupil:**
The pupil is the black circular opening in the center of the iris. It allows light to enter the eye and reach the retina, where it is processed and transmitted as visual information to the brain. The size of the pupil can change in response to different lighting conditions and the body's need for visual acuity.

**Function of Iris and Pupil:**
The iris and pupil work together to regulate the amount of light entering the eye. In bright light, the sphincter muscle in the iris contracts, causing the pupil to constrict or become smaller. This reduces the amount of light entering the eye and prevents excessive light from reaching the retina, which could cause discomfort or damage.

On the other hand, in dim light, the radial muscle in the iris contracts, causing the pupil to dilate or become larger. This allows more light to enter the eye, improving visibility in low-light conditions.

The ability of the iris and pupil to adjust the size of the pupil is called the pupillary reflex. It is an involuntary response controlled by the autonomic nervous system, which regulates bodily functions without conscious control.

In summary, the combination responsible for admitting different amounts of light into the eye is the iris and pupil. The iris controls the size of the pupil, while the pupil allows light to enter the eye. Together, they regulate the amount of light reaching the retina, ensuring optimal visibility in different lighting conditions.