With the exception of the 12 cranial nerves, other major nerves exit the brain through the:

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.