Which of the Following Was a Key Obstacle That Hominins

Which of the following was a key obstacle that hominins' increase in brain size had to overcome?

A) larger skulls demanding more elastic birth canals, even though the requirements of skeletal development during a woman's lifetime limit the elasticity of birth canals
B) the challenges of walking with a head that is too heavy
C) overcoming the trend of clumsy locomotion that makes hominins vulnerable to predators
D) overcoming the trend of ever more self-sufficient children eager to separate themselves from their mothers
E) larger skulls demanding larger birth canals, even though the requirements of upright bipedalism impose limits on the expansion of the human pelvic opening