单项选择题

Questions 23 to 25 are based on the conversation you have just heard.

A．Careers in environmental engineering.
B．A way to improve fuel efficiency in buses.
C．The causes of air pollution.
D．A new fuel for buses.
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单项选择题
A．How bones continuously repair themselves.B．The chemical composition of human bones.C．Two different types of bones in the human body.D．How bones help the body move.
A．How bones continuously repair themselves.
B．The chemical composition of human bones.
C．Two different types of bones in the human body.
D．How bones help the body move.
单项选择题
A．1:30.B．9:30.C．11:00.D．10:30.
A．1:30.
B．9:30.
C．11:00.
D．10:30.
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