Imagine that you adapted to a motion stimulus with one eye and then switched to the other eye and did not experience a motion aftereffect in that eye. This lack of interocular transfer implies that the locus of the motion aftereffect is:

Explanation:

The lack of interocular transfer implies that the locus of the motion aftereffect is before V1

V1 is the the primary visual cortex which is located in the most posterior portion of the brain's occipital lobe

A large part of the primary visual cortex cannot be seen from the outside of the brain, because this cortex lies on either side of the calcarine fissure

This fissure, however, is clearly visible in a sagittal section made between the two cerebral hemispheres

Area V1 contains a complete map of the visual field covered by the eyes

It receives its main visual input from the lateral geniculate nucleus of the thalamus (LGN), and sends its main output to subsequent cortical visual areas

i think the answer is b.