Explanation:

The human eyeball is composed of three primary layers:

1. Sclera: This is the outermost layer, a tough protective coating that gives the eye its white color.

2. Choroid: Situated just inside the sclera, this layer is rich in blood vessels to provide nourishment to the eye.

3. Retina: The innermost layer, containing light-sensitive cells that convert light into neural signals for vision.

The cornea is part of the scleral layer at the front of the eye. Therefore, the correct sequence from exterior to interior is sclera, choroid, and retina.

Answer: Option 1 - Sclera --> Choroid --> Retina