【单选题】第三篇 Why Humans Walk on Two Legs A team of scientists that studied chimpanzees(黑猩猩)trained to use treadmills (跑步机) has gathered new evidence suggesting that our earliest apelike ancestors started walki...
A.
where humans came from.
B.
how chimpanzees could be trained to use treadmills.
C.
when our earliest ancestors began to live in forested areas
D.
why our apelike ancestors came to walk on two legs.