On the back of your skull, you can feel a small bump, below which is an opening where the spinal cord enters the skull.

On the back of your skull, you can feel a small bump, below which is an opening where the spinal cord enters the skull. The location of this opening toward the bottom of the skull is significant in evolutionary biology for what reason?

A. It allowed for the hominid brain to grow much larger than other primates

B. It occurred as a result of the change to a bipedal stance

C. It provided greater protection for the spinal cord

D. This change was necessary for the increase in size from prosimian forms to anthropoid forms

Please explain why B is the correct answer, and not C.