How did mary leakey's discovery change the modern understanding of prehistoric humans?

a. the bone she found provided evidence that early hominids made tools in east africa almost 2 million years ago

b. the skeleton she excavated prove that early hominids walked upright and we're almost four feet tall

c. the artifacts you discovered offered evidence that early hominids lived in ethiopia about 3 million years ago

d. the remains she dug up at olduvai gorge first homo erectus were the first to use tools