On the Back of the Human Skull, There Is a Small

On the back of the human skull, there is a small bump, below which is an opening where the spinal cord enters the skull. Which of the following statements provides the best evolutionary explanation for the location of the opening near the base of the skull?

A) It allowed for the hominin brain to grow much larger than other primates.
B) It provided greater protection for the spinal cord.
C) It is associated with the change to a bipedal stance.
D) This change was necessary for the increase in size from prosimian forms to anthropoid forms.