Final answer:
The structure that lies inside and parallel to the sclera is the choroid (option 3), which is a highly vascularized connective tissue providing blood supply to the eyeball.
Step-by-step explanation:
The structure that lies inside and parallel to the sclera is the choroid. The sclera is the outermost layer of the eye and is known as the white part of the eye. Beneath the sclera is the vascular tunic which includes the choroid as well as the ciliary body and iris. The choroid is highly vascularized connective tissue that provides blood supply to the eyeball and lies between the sclera and the retina. The choroid is essential for nourishing the outer part of the retina with blood, and it plays a key role in the eye's ability to function properly.