The correct option is B white matter
The central nervous system comprises of brain and the spinal cord. They are covered 3 layers of meninges for protection. The 3 layers of meninges are - dura mater, arcahnoid mater and pia mater.
The brain is divided into - forebrain, midbrain and hindbrain.
The forebrain is divided into 3 parts - cerebrum, thalamus and hypothalamus. The outer layer of the cerebrum is thrown into folds and is called the cerebral cortex. The outer layer of the cortex is also known as the white matter due to the presence of neuronal cell bodies. The inner layer is called white matter due to the presence of myelinated axons of the above mentioned neuronal cell bodies.