(B) is the right answer.
The adult human eye ball is nearly a spherical structure. The wall of the eye ball is composed of three layers. The external layer (among three layers of eye) is composed of a dense connective tissue and is called the sclera. The anterior portion of this layer is called the cornea. The middle layer, choroid, contains many blood vessels and looks bluish in colour. The choroid layer is thin over the posterior two-thirds of the eye ball, but it becomes thick in the anterior part to form the ciliary body.