Answer:
The answer is Letter B. It is the only true affirmation.
Explanation:
The cerebral hemispheres account for about 83% of total brain mass.
The other alternatives are false because the longitudinal fissure is the deep groove that separates the two hemisphere of the vertebrate brain.
Gyri is not the shallow groove that mark the nearly entire surface of he cerebral hemispheres. Gyri is a ridge on the cerebral cortex.
Sulci is not the elevate ridge that marks nearly the entire surface of the cerebral hemisphere. Sulci is a depression that surrounds the cerebral cortex.
The Gyri and the Sulci create the folded appearence of the human brain and some other mammals.