Passage Two
Questions 30 to 32 are based on the passage you have just heard.

A．They lived in caves.
B．They didn’t have their language.
C．They could only build houses with animal bones and skins.
D．They were advanced beyond our expectation.

A．The problems of environment pollution.
B．A material which can save fuel.
C．The installation of pollution filters.
D．The way to spray a coat on the engines.