Bipedalism Is Believed to Have Evolved in the Hominid Lineage

Bipedalism is believed to have evolved in the hominid lineage because bipedal locomotion is

A) more efficient than quadrupedal locomotion.
B) more efficient than quadrupedal locomotion and frees the forelimbs to manipulate objects.
C) less efficient than quadrupedal locomotion but frees the forelimbs to manipulate objects.
D) less efficient than quadrupedal locomotion,but bipedal animals can run faster.
E) less efficient than quadrupedal locomotion,but natural selection does not act to improve efficiency.