Final answer:
The Metencephalon is a major embryological grouping of the brain that forms the pons, cerebellum, and medulla oblongata in the adult brain.
Step-by-step explanation:
The Metencephalon is a major embryological grouping of the brain that develops from the rhombencephalon. It forms the adult structures known as the pons, cerebellum, and the medulla oblongata. Therefore, the correct answer to all three options (A, B, and C) would be option 3) Both A and B.