Which part of the eye is transparent and allows light to enter?

The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. It plays a crucial role in vision by allowing light to enter the eye and bending (refracting) it to help focus images on the retina. The cornea provides about two-thirds of the eye's total optical power.

Unlike other parts of the eye, such as the sclera, which is opaque and serves as protective outer covering, or the retina, which is primarily responsible for converting light into neural signals but does not allow light to pass through, the cornea's unique structure allows it to be clear and effective in its function. The iris, while it controls the size of the pupil and thereby regulates the amount of light that enters the eye, is not transparent. Hence, the cornea is the correct choice in this context.