The correct option is A Elephant
The corpus callosum also callosal commissure is a wide commissure, a flat bundle of commissural fibers, about 10 cm long beneath the cerebral cortex in the brains of the placental mammals. The brain is divided into a right and left hemisphere, and the two halves are connected by the corpus callosum in the mammalian brain. Since in the list given elephant is the only mammal, the correct option is A.