题目内容：
Why did the chimpanzees walk on two limbs during Kyoto University's experiment__________?
A．Because they imitated the human way of walking just for fun. B．Because they wanted to please the researchers to get more coula nuts from them.
C．Because they wanted to get to the nut-rich forest faster -- by walking that way.
D．Because they wanted to carry more nuts with two free limbs.
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