Which part of the eye consists of the sclera, cornea, and limbus?

The fibrous tunic is the correct answer because it is the outermost layer of the eye and comprises both the sclera and the cornea, as well as the limbus, which is the border area between the sclera and cornea. The sclera provides structural support and protects the inner components of the eye, while the cornea serves as a transparent window that allows light to enter and begins the process of focusing it. The limbus plays a crucial role in the health of the eye by providing a transition between the clear cornea and the opaque sclera, as well as housing stem cells that help regenerate the cornea.

The vascular tunic, also known as the uvea, includes the iris, ciliary body, and choroid, which are responsible for providing nourishment to the eye and controlling light entry but do not comprise the outer layer mentioned in the question. The neural tunic refers to the retina, which is responsible for light detection and vision. Aqueous humor is the fluid within the anterior segment of the eye that helps maintain intraocular pressure but is not a part of the eye's structural layers.