Since the earliest times, trees have always been very useful and important to man who made use of them in many ways. Even today trees continue to serve man in so many ways.　Trees provide man with fruits and building materials in the form of wood. W

Since the earliest times, trees have always been very useful and important to man who made use of them in many ways. Even today trees continue to serve man in so many ways.　Trees provide man with fruits and building materials in the form of wood. W
Since the earliest times, trees have always been very useful and important to man who made use of them in many ways. Even today trees continue to serve man in so many ways.　
Trees provide man with fruits and building materials in the form of wood. Without trees it would be impossible to build houses, boats and even bridges. Furniture such as tables, chairs and beds is made of wood.　
In the tropics where it is very hot throughout the year, trees protect man from the terrible heat. They are also useful in preventing good and rich top soil from being washed away during heavy rains which are so common in the tropics.　
If there were no trees or vegetation of some kind to hold back the soil with their roots, heavy rain would wash away the rich surface soil that is so important and necessary to agriculture. The result is that the land becomes a desert.　
There are so many desert areas in the world. A long time ago these desert areas must have been very rich fertile areas, but since our ancestors in the distant past did not have enough knowledge about science of nature, they cut down all the trees in the areas where they lived and never planted new ones. By and by, the rich surface soil was blown away and washed away by strong winds and heavy rains. In the end the land was turned into useless deserts where nothing could grow.
31. According to the passage,______.
A. ancient man did not know how to make use of trees
B. trees are not as useful now as they were in the pas
C. trees are more useful in the past than they are now
D. men have always found trees very useful
32. According to the passage, some desert areas were once ______.
A. fertile lands B. covered by icebergs
C. very cold D. very dry and useless lands
33. If there were no trees,______.
A. the land would become more fertile
B. heavy rains would clean the tropics
C. the rich top soil couldn’t be held back
D. the balance of nature is unimportant to man
34. From this passage, we know that ______.
A. man can do nothing to keep the balance of nature
B. man may take no notice of the balance of nature
C. man must do his best to keep the balance of nature
D. the balance of nature is unimportant to man
35. The best title of this passage is ______.
A. The Uses and Importance of Trees B. The Importance of Top Soil
C. How Are Rich Lands Turned into Deserts D. Keep the Balance of Nature

Since the earliest times, trees have always been very useful and important to man who made use of them in many ways. Even today trees continue to serve man in so many ways.　Trees provide man with fruits and building materials in the form of wood. W
31.根据第一段内容选D 人们一直认为树木是有用的
32.根据最后一段原句选A
33.倒数第一、二段选C 没有树木表层肥沃的土壤都会被冲走
34.最后一段选B人类祖先没有意识到大自然的平衡性的
35.选A,文章主要讲树的,而不是沙漠