The right answer is A. optic chiasm.
The optic chiasm is the part of the brain where the two optic nerves intersect. Each retina is divided into two hemiretins (an internal nasal and an external temporal), the optical pathways of the nasal hemiretins undergoing a decussation (change of side) in the chiasma.
The optical chiasm allows the decussation of a number of axons from the retina, that is to say their change of side to ensure the cross processing of visual information. It is therefore the place where the visual information of the same half-field is collected by the two retinas. This organ located under the encephalon (anterior part) thus allows the stereoscopy (interpretation of the relief).
