What Do the Discoveries in the Awash River Valley Suggest

What do the discoveries in the Awash River valley suggest about the environment where bipedalism appeared in early hominids?

A) Early hominids lived exclusively on the African savanna.
B) Early hominids lived exclusively in wooded regions.
C) Early hominids lived only in wooded regions along lakes.
D) Early hominids may have lived in wooded regions along lakes, as well as on the savanna.