题目内容：
How do we explain that human beings have the ability to speak according to biologists?
A．.It is hard to say. A．It is hard to say.
B．There are speech mechanisms that function in our brain.
B．There are speech mechanisms that function in our brain.
C．We acquire the ability by learning from others.
C．We acquire the ability by learning from others.
D．There is a speech machine that can work in our brain.
D．There is a speech machine that can work in our brain.
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答案解析：