Passage Three
Questions 33 to 35 are based on the passage you have just heard.

A．They are handed down generation after generation.
B．People can buy them with large amount of money.
C．They are preserved in libraries and bookstores.
D．Most of them are lost year by year.

A．Supporting the soil.
B．Providing shade for animals.
C．Loosening soil structure.
D．Protecting the soil from wind and rain damage.