Hay cuatro tipos diferentes de nucleótidos de DNA: adenina (A), timina (T), guanina (G), citosina (C).
I think the answer should be medulla oblongata or foramen magnum.
The major nerves that leave brain should form a thick cord in the brain stem that called medulla oblongata. Medulla oblongata will pass a big hole in the base of the skull that called foramen magnum. Depends on what part the question asked(bone or tissue), it probably between those two options.
Carbon and fluorine combine covalently to form a binary compound. the formula of the compound with the name carbon tetrafluoride is CF4.