In1620，abouthalftheUSAwascoveredbyforests．In1850，aboutathirdwascoveredbyforests．Todaytheforestshavealmostgone．Alotgoodlandhasgonewiththem，leavingonlysand．TodaytoomanytreesarestillbeingcuttheUSA．Ch

Question

In 1620，about half the USA was covered by forests．In 1850，about a third was covered by forests．Today the forests have almost gone．A lot good land has gone with them，leaving only sand．Today too many trees are still being cut the USA．
China does not want to copy the USA's example．So China has built a new Great Wall across the northern part of the country．This time it is a"Great Wall"of trees，millions of trees．
The Great Green Wall is 7，000kilometers long，and between 400and 1，700kilometers wide．The Great Green Wall will stop the wind from blowing the earth away．It will stop the sand from moving towards the rich farmland in the south．It has already saved a lot of land．But more"Great Green Walls"are still needed，and not only in China．They must be built all over world．
31．About___ the USA's forests went from 1620to 1850．
A．halfB．a thirdC．a sixthD．one eighth
32．If too many tree are cut down in a place，___．
A．a lot of good land will go and much sand will be left
B．a lot more farmland will be got
C．many more plants will be grown
D．more house will be built
33．China has built the Great Green Wall because___．
A．it does not want to copy the example of the USA
B．there is not enough farmland
C many trees are still needed
D．the Great Wall is old and broken
34．The Great Green Wall is made of___．
A．metal    B．wood     C．trees   D．bricks
35．China built the Great Green Wall to___．
A．meet people's need for more treesB．save the land
C．grow a lot more foodD．make good use of mountain．

Answer 1

31．C细节理解题．根据第一段In 1620，about half the USA was covered by forests．In 1850，about a third was covered by forests可知在1620，大约一半的美国被森林覆盖着．在1850，大约有三分之一被森林覆盖，即1620年到1650有大约六分之一森林消失了，故选C．
32．A细节理解题．根据第一段Today the forests have almost gone．A lot good land has gone with them，leaving only sand可知良田随着森林的消失而消失，只剩下沙子，故选A．
33．A细节理解题．根据第二段China does not want to copy the USA's example．So China has built a new Great Wall across the northern part of the country可知中国不希望复制美国的例子，已经在北部建立了一个新的绿色长城，故选A．
34．C细节理解题．根据第二段This time it is a"Great Wall"of trees，millions of trees可知绿色长城是由树构成的，故选C．
35．B细节理解题．根据第三段The Great Green Wall will stop the wind from blowing the earth away．It will stop the sand from moving towards the rich farmland in the south可知中国建造绿色长城是为了保持水土，故选B．