The outside of the eye is covered by a tough membrane known as which of the following?

The sclera is the correct answer because it is the tough, white outer layer of the eyeball that provides protection and structural support. This dense connective tissue is continuous with the cornea at the front of the eye. The sclera plays an important role in maintaining the shape of the eye and serves as an attachment point for the muscles that move the eye. Its sturdy composition helps safeguard the inner components of the eye from injury.

While the choroid, retina, and cornea are all essential parts of the eye, none of these serve the same protective function as the sclera. The choroid is a layer that contains blood vessels and provides nourishment to the eye, the retina is the light-sensitive layer where images are formed, and the cornea is the transparent front part of the eye that helps focus light. Each of these structures contributes to vision and eye function, but it is the sclera specifically that is recognized for its tough, protective qualities.