Questions: Oxygen and nutrients are delivered to the outer portion of the retina by an extensive capillary network contained within the ora serrata choroid sclera ciliary body macula

The answer is the second one (or B): choroid.

Explanation for each option:

1. Ora serrata: This is the serrated junction between the retina and the ciliary body. It does not contain an extensive capillary network for delivering oxygen and nutrients to the outer portion of the retina.
2. Choroid: The choroid is a vascular layer of the eye containing connective tissues and lying between the retina and the sclera. It is rich in blood vessels and provides oxygen and nutrients to the outer layers of the retina.
3. Sclera: This is the white outer layer of the eyeball. It is primarily a protective layer and does not contain the capillary network needed for nourishing the retina.
4. Ciliary body: This structure includes the ciliary muscle and ciliary processes, which are involved in the accommodation of the lens and production of aqueous humor, but it does not supply the outer retina with nutrients.
5. Macula: This is a small central area of the retina that is responsible for detailed central vision. It does not contain the extensive capillary network for the outer retina.

Summary: The choroid is the correct answer because it contains the extensive capillary network that delivers oxygen and nutrients to the outer portion of the retina.