Why Is the Advent of Bipedalism Considered Such a Significant

Why is the advent of bipedalism considered such a significant event in human evolution?

A) Because only bipedal organisms have large brains, indicating that they are capable of becoming intelligent
B) Because bipedalism initiated a cascade of evolutionary events that resulted in the evolution of our large brains
C) Because standing upright helped our ancestors evade predators
D) Because the morphological adjustments required for bipedalism resulted from genetic changes that also resulted in cranial evolution, allowing for a larger brain case.