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.
Answer:
e. All could limit protein mobility
Explanation:
Plasma membrane proteins perform a variety of functions: they act preferentially on transport mechanisms, organizing true tunnels that allow substances to pass into and out of the cell, function as membrane receptors, among other functions. These proteins vary greatly in their mobility, some are as mobile as lipids, while others are practically immobile. But FRAP has revealed that some proteins move in cell membranes much more slowly than in reconstituted liposomes. This limited mobility can be explained by the statement in alternative "E" of the above question.