What is the pupil's function in the eye?

The pupil serves as the opening through which light enters the eye. It is a crucial feature of the eye's anatomy, allowing light to pass through and reach the retina, where images are formed. The size of the pupil can change in response to light levels, constricting in bright light and dilating in low light conditions, which helps control the amount of light that enters the eye. This function is essential for optimal vision in varying lighting conditions.

While other options may describe functions related to different parts of the eye, the direct role of the pupil is specifically to control light entry, making it the correct answer.