Concept: This question tests your knowledge of the gross anatomy of the brain, specifically the organization of the cerebral cortex and its underlying structures.

Why (A) is correct: The cerebral cortex is the outermost layer of the cerebrum. The inner part, beneath the gray matter of the cortex, is primarily composed of myelinated axons, which form the white matter. These myelinated axons are responsible for transmitting signals between different areas of the brain and between the brain and the rest of the body.

Why other options are wrong:

• (B) Gray matter: Gray matter forms the outer layer (cortex) of the cerebrum and consists mainly of neuron cell bodies, dendrites, unmyelinated axons, and glial cells.
• (C) Both (A) & (B): This is incorrect because the inner part is predominantly white matter, while the outer part is gray matter.
• (D) Non-myelinated nerve fibres: While non-myelinated nerve fibres are present in the brain, they are primarily found in the gray matter, not forming the bulk of the inner part of the cerebrum.

Common Mistake: Students often confuse the location of gray and white matter in the brain versus the spinal cord. In the brain, gray matter is superficial (cortex) and white matter is deep. In the spinal cord, gray matter is central (H-shaped) and white matter is superficial.

NEET Tip: Remember the mnemonic 'G-O-W-I' for the brain: Gray matter Outside, White matter Inside.

Correct Answer: (A)