B．increasing the production of grain harvests

　　C．providing humans with shade from the sun

　　D．reducing the damaging effects of wind and rain

　　解析：选C　细节理解题。根据第一段第三句"They also keep the wind from damaging or destroying crops."可排除A项；根据第二段第二句"... grain harvests were twenty percent higher in fields protected by windbreaks ..."可排除B项；根据最后一段倒数第三句"Trees reduce the damaging effects of wind and rain."可排除D项。故答案为C项。

　　6．The author thinks windbreaks are interesting because ________.

　　A．the movement of air lifts the soil

　　B．windbreaks allow some wind to pass through

　　C．large trees are lined with short ones

　　D．windbreaks can stop the wind getting through

　　解析：选B　细节理解题。根据第三段的前四句可知，防护林的有趣之处在于它可以允许一些风穿过防护林，从而防止土壤流失，故答案为B项。

　　7．If the trees grow to a height of 30 feet, the areas the windbreak can protect are ________.

　　A．100 square feet B．151 square feet

　　C．240 square feet D．300 square feet

　　解析：选D　推理判断题。根据第三段最后一句"... windbreaks can protect areas up to 10 times the height of ..."可知，30英尺高的防护林可以保护300平方英尺地区，故答案为D项。

　　8．What can be inferred from the text?

　　A．Extra trees and plants can be out down for wood.

　　B．The environment is going from bad to worse.

　　C．Trees and plants from abroad are the best for windbreaks.

　　D．Windbreaks can contribute to agriculture harvests.

　　解析：选D　推理判断题。根据第二段对于西非的介绍可推知防护林可以促进农业的丰收，故答案为D项。

　　C

　　Gardens in Scotland

　　Dirleton Castle

　　The garden at Dirleton, dating from the 16th century, now is a mixture of formal tradition and modern plantings. Recognized by the Guiness Book of World Records as having the world's longest herbaceous (草本的) border.

Location：3 m W North Berwick, on A198