The correct option is A Pons Varolii
The pons Carolla is a mass of transverse nerve fibers that connect the medulla oblongata with the cerebellum. Arborvitae is the cerebellar white matter. Cerebral hemispheres are the two parts of the cerebrum separated by a longitudinal fissure. Medulla oblongata is the lowest portion of the brain stem. So, the correct option is 'Pons Varolli'.