Answer:
C. Standing upright allowed for sightlines over tall grasses and savanna shrubbery
Step-by-step explanation:
One of the most accepted theories about the development of bipedalism of the hominids is that it was mostly because of the tall grasses and shrubs, so standing upright was providing them with better view. Once the environment changed, and the tropical rainforest was turned into savanna, the hominid ancestors had to adapt in order to survive. Being helpless against the large predators, they needed something in order to be able to detect them from bigger distance so that they can avoid them. The solution seemed to be to be able to see above the tall grasses and shrubs, which meant that they started to use their legs more and more in order to stand up taller. This gradually led to better development of legs for upright standing and walking, also causing changes in the structure of the body, providing the hominids with an adaptation that enabled them to survive in the very dangerous environment.