Passage Three Trees should only be pruned （修剪) when there is a good reason for doin

阅读材料，回答题。

Trees are useful to man in three important ways: they provide him with wood and other products; they give him shade; and they help to prevent droughts and floods.

Unfortunately, in many parts of the world, man has not realized that the third of these services is the most important. In his eagerness to make money from trees, he has cut them down in large numbers, only to find that without them he has lost the best friends he had. And besides, he is usually too careless to plant and look after new trees. So the forests slowly disappear.

This does not only mean that man will have fewer trees. The results are even more serious for where there are trees, their roots break up soil allowing the rain to sink in and also bind the soil, thus preventing it from being washed away easily; but where there are no trees, the rain fall son hard ground and flows away, causing floods and carrying away the rich topsoil. When all the topsoil is gone, nothing remains but worthless desert.

Two thousand years ago a rich and powerful country cut down its trees to build warships, with which to gain itself an empire. It set up the empire but, without its trees, its soil became poor and it grew weak. When the empire fell to pieces, the home country found itself faced with floods and starvation.

What is the most important service of trees to man according to the passage？ 查看材料

A.They help him make money

B.They give him wood and other products

C.They help him prevent droughts and floods

D.They give him shade

Trees mainly serve man in three important ways: They provide him with wood and other products; they provide him shade; and they help to prevent droughts and floods.Unfortunately, in many parts of the world, man has not realized that the third of these services is the most important.In his eagerness to make money from trees, he has cut them down in large numbers, only to find that without them he has lost the best friends he had. And besides, he is usually too careless to plant and look after new trees. So the forests slowly disappear.This does not only mean that man will have fewer trees. The results are even more serious: for where there are trees, their roots break up soil allowing the rain to sink in and also bind(固定) the soil, thus preventing it from being washed away easily;but where there are no trees, the rain falls on hard ground and flows away, causing floods and carrying away the rich top-soil. When the top-soil is gone, nothing remains but worthless desert.Two thousand years ago，a rich and powerful country cut down its trees to build warships, with which to gain itself an empire.It set up the empire, but, without its trees, its soil became poor and grew weak. When the empire fell to pieces, the home country found itself faced by floods and starvation(饥荒).

A、Trees and Man

B、The Function of Tree Wood

C、How do People do with Trees

D、The Usage of Tree Roots

These apple trees, ______I planted three years ago, have not borne any fruit.

A．that

B．what

C．which

D．when

A.beautiful

B.healthy

C.old

D.young

According to the passage, which of the following can NOT be typed into the same category？

A． Cloud

B． Sheep

C． Trees

D． Goose

understanding of how many stars there are in the galaxy than how many species there are on Earth？ Their estimates of global species diversity vary from 2 to 100 million species. Most people agree on an estimate of somewhere near 10 million and yet only 1.75 million have actually been named. Current knowledge of species diversity is limited. This problem becomes more serious because there is a lack of a central database or list of the world’s species.

New species are still being discovered — even new birds and mammals(哺乳动物). On average, about three new species of birds are found each year, and since 1990, 10 new species of monkeys have been discovered. Other groups are still far from being completely described: an estimated 40 percent of freshwater fishes in South America have not yet been classified.

Scientists were startled in 1980 by the discovery of a huge diversity of insects in tropical forests. In one study of just 19 trees in Panama, 960 new species of beetles were discovered.

As scientists begin investigating other little-known ecosystem, like the soil and the deep sea, “surprising” discoveries of species become commonplace. There is nothing strange about this, though, since as many as a million undescribed species are believed to live in the deep sea. And one gram of a small-sized piece of land might hold 90 million bacteria(菌类) and other microbes(微生物). How many species these communities contain is still anyone’s guess.

16. Which of the following is true？

A) Scientists have a sound knowledge about the diversity of species

B) Scientists don’t know much about the number of stars in the galaxy

C) Scientists show more interest in stars in the galaxy than in species on Earth

D) Scientists don’t agree on the number of species in the world

17. How many species are there on Earth according to most scientists？

A) About 2 million

B) About 10 million

C) About 100 million

D) About 1.75 million

18. In which of the following groups is the discovery of new species not mentioned in

the passage？

A) Birds

B) Monkeys

C) Trees

D) Freshwater fish

19. What can you learn from the passage？

A) The soil and the deep sea belong to communities that haven’t been fully explored

B) It is surprising news wherever new species are discovered in the deep sea

C) About 90 million species are believed to live in the deep sea

D) A million species in the deep sea have been discovered and named

20. Which of the following best reveals the main idea of the passage？

A) Surprising discoveries of new species are commonplace

B) The mystery of the deep sea and the soil remains to be uncovered

C) Knowledge of global species diversity is still limited

D) Estimates of global species diversity vary among scientists

Flying over a desert area in an airplane, two scientists looked down with their trained eyes at trees and bushes

A.How trees help prevent droughts and floods.

B.The relationship between trees and man.

C.How an empire fell to pieces in ancient times.

D.A story of trees.

A．Scientists Searching for Metals with Special Power

B．New Methods of Searching for Trees and Bushes

C．Gold Could Be Found by Trees and Plants

D．A New Method of Searching for Minerals: Using Trees and Plants

This newest method of searching for minerals is based on the fact that minerals deep in the earth may affect the kind of trees and bushes that grow on the surface