Plants can’t communicate by moving or making sounds, as most animals do. Instead, plants Produce volatile compounds, chemicals that easily change from a liquid to a gas. A flower’s sweet smell, for example, comes from volatile compounds that the plant produces to attract insects such as Bugs and bees.

Plants can also detect volatile compounds produced by other plants. A tree under attack by Hungry insets, for instance, may give off volatile compounds that let other trees know about the Attack. In response, the other trees may send off chemicals to keep the bugs away ——or even  Chemicals that attract the bugs’ natural enemies.

Now scientists have created a quick way to understand what plants are saying: a chemical Sensor（传感器）called an electronic nose. The “e-nose” can tell compounds that crop plants make When they’re attacked Scientists say the e-nose could help quickly detect whether plants are being Eaten by insects. But today the only way to detect such insects is to visually inspect individual Plants. This is a challenging task for managers of greenhouses, enclosed gardens than can house Thousands of plants.

The research team worked with an e-nose than recognizes volatile compounds. Inside the device, 13 sensors chemically react with volatile compounds Based on these interactions, the e-nose gives off electronic signals that the scientists analyze using computer software.

To test the nose, the team presented it with healthy leaves from cucumber, pepper and tomato plants, all common greenhouse crops. Then scientists collected samples of air around damaged leaves from each type of crop, These plants had been damaged by insects, or by scientists who made holes in the leaves with a hole punch（打孔器）. The e-nose, it turns out, could identify healthy cucumber, pepper and tomato plants based on The volatile compounds they produce, It could also identify tomato leaves that had been damaged. But even more impressive, the device could tell which type of damage ---- by insects or with a hole Punch ---- had been done to the tomato leaves.

With some fine-tuning, a device like the e-nose could one day be used in greenhouses to quickly spot harmful bugs, the researchers say. A device like this could also be used to identify fruits that are perfectly ripe and ready to pick and eat, says Natalia Dudareva, a biochemist at Purdue University in West Lafayette, Ind. who studies smells of flowers and plants. Hopefully, scientists believe, the device could bring large benefits to greenhouse managers in the near future.

1.We learn from the text that plants communicate with each other by____.

A. making some sounds        B. waving their leaves

C. producing some chemicals   D. sending out electronic signals

2.What did the scientists do to find out if the e-nose worked?

A. They presented it with all common crops.

B. They fixed 13 sensors inside the device.

C. They collected different damaged leaves.

D. They made tests on damaged and healthy leaves.

3.According to the writer, the most amazing thing about the e-nose is that it can___.

A. pick out ripe fruits

B. spot the insects quickly

C. distinguish different damages to the leaves

D. recognize unhealthy tomato leaves

4.We can infer from the last paragraph that the e-nose_____.

A. is unable to tell the smell of flowers

B. is not yet used in greenhouses

C. is designed by scientists at Purdue

D. is helpful in killing harmful insects

The year is 2094. It has been announced that a comet (彗星) is heading towards the Earth . Most of it will miss our planet, but two pieces will probably hit the southern half of the Earth.

  On 17 July , a piece four kilometers wide enters the Earth’s atmosphere (大气层) with a massive explosion . About half of the piece is destroyed, but the remaining part hits the South Atlantic at 200 times the speed of sound. The sea boils and a huge hole is made in the sea bed. Huge waves are created and spread outwards from the hole. The wall of water, a kilometer high, rushes towards southern Africa at 800 kilometers an hour. Cities on the African coast are totally destroyed and millions of people are drowned.

Before the waves reach South America, the second piece of the comet lands in Argentina. Earthquakes and volcanoes are set off in the Andes Mountains. The shock waves move north into California and all around the Pacific Ocean. The cities of Los Angeles, San Francisco and Tokyo are completely destroyed by earthquakes. Millions of people in the southern half of the earth are already dead, but the north won’t escape for long. Because of the explosions, the sun is hidden by clouds of dust, temperatures around the world fall to almost zero .Crops are ruined. The sun won’t be seen again for many years. Wars break out as countries fight for food. A year later, no more than 10 million people remain alive.

Could it really happen? In fact, it has already happened more than once in the history of the Earth. The dinosaurs were on the Earth for over 160 million years. Then 65 million years ago they suddenly disappeared. Many scientists believe that the Earth was hit by a piece of object in space. The dinosaurs couldn’t live through the cold climate that followed and they died out. Will we meet the same and?

What is mainly described in the passage?

 A．A historic discovery.     B．An event of imagination

 C．A research on space.     D．A scientific adventure.

When the first piece hits the South Atlantic, it causes  ________  .

 A．an earthquake           B．damages to cities

 C．an Earth explosion       D．huge waves

Why can’t the northern half of the earth escape for long?

 A．Because the land is covered with water

 B．Because the light and heat from the sun can not reach the earth.

 C．Because people there can not live at the temperature of zero.

 D．Because wars break out among countries.

By giving the example of dinosaurs, the author tries to prove ________ .

 A．animals could not live in the cold climate

 B．what happened 65 million years ago was an invented story

 C．the human beings will die out in 2094

 D．the Earth could be hit by other objects in space

If you want your land to keep fertile, you must try to stop soil from being carried away by water or wind. When soil is taken away by flowing water or blowing winds we call it soil erosion. Ways have been found to stop soil erosion, and this is known as soil conservation. One way of stopping soil erosion is to grow small plants such as grass. These plants are referred to a cover crops, whose roots hold the soil tightly together. The rain water can not wash away the soil. When trees and tall bushes are planted at the edges of an open field, soil erosion by strong winds can not take place. The trees and bushes, which act as a very big and firm wall, protect the open land from the winds. The way to stoop soil erosion on slopes is to build terraces on the slope of hillside and mountainside. When the slope of a hillside is cut into “step”, water carrying soil can not run straight down the terraces, which are used to slow down the speed of the flowing water containing much soil in it. In this way most of the soil in the water is left behind on the terraces, much soil in it.

1.What takes place in soil erosion?

A.   Flood happens to the fertile land

B.    A large quantity of the soil loses away gradually.

C.    Terraces are built on the slope of hillside or mountainside.

D.   Plants are grown to protect the open land

2.“Cover crops” in this passage means _________.?

A. grass        B. trees and bushes     C. plants life and an area

E.    covering plants that produce grain or vegetables

3.Besides growing small plants, another method to fight against soil erosion is to ___________.

A. build terraces  B. build walls    C. plant trees    D. plant tall bushes

4.According to the passage, trees and tall bushes are planted around an open field ________________.

A.       because their roots hold soil tightly

B.        to stop soil from being blown away by winds.

C.        Because soil erosion causes terrible damages to crops

D.       To keep the balance of nature

5.Which of the following is the best title of the passage?

A. What Causes Soil Erosion

B. The Importance of Erosion

C. Rain Erosion and Wind Erosion

D.Erosion and the Way of Tight against Erosion

In today’s world, we rely on computers as never before. They are used for everything from ordering a pizza to running hospitals and military defense systems. Banking and credit card information is stored and accessed by computers. So what happens when a computer gets infected with a virus? One effect is that people’s access to their e-mail accounts is cut off. A more serious possible consequence is that billions of dollars could be lost.

A virus is a computer program that copies itself onto other programs and infects them. Similar to an easily spread disease, a computer virus goes from computer to computer, either adding to or changing the tasks a program is designed to do.

The first computer viruses were created in the mid’80s and had varying effects. Some caused files to be deleted, or made the letters on the screen appear to fall off. Others displayed a specific message once the computer was turned on.

Viruses today are much more widespread and dangerous than ever before. Perhaps the most damaging has been the “I Love You” virus. “I Love You” appeared in May 2000 and has possibly been the most destructive virus in terms of monetary loss.

The virus is released（释放） when an attachment（附件） to a fake e-mail message is opened. By changing the names of files on computers, “I Love You” makes them difficult to access. It also searches for important personal information, including passwords, which it sends to a Web site for others to see.

It is estimated that more than 45 million people in 20 countries have had their computers infected by the “I Love You” virus. Some say the cost of repair and lost business has been more than US$10 billion.

If you own a computer, it is important to keep it in good health by installing（安装） an anti-virus program. If updated frequently, it will protect your e-mail access-----not to mention your wallet.

51. What does “virus” mean in the article?

A. An easily spread disease.

B. A contagious (传染的) computer program.

C. An extremely small organism（微生物）which causes disease.

D. A parasite（寄生虫）in computer.

52. How dose “I Love You” virus spread?

A. It is spread when an e-mail account is opened.

B. It is spread through on-line chatting.

C. It is spread through e-mail.

D. It spread from web site to web site.

53. Which of the following is one of the damages brought by “I Love You” virus?

A. It deletes files.

B. It automatically turns on computers.

C. It automatically turns off computers.

D. It makes it difficult to access files.

54. Which of the following is the best way to guard against virus?

A. To load an up-to-date anti-virus program into our computer.

B. Not to use an e-mail account.

C. To upgrade our computer.

D. Not to use the Internet.

55. What is the purpose of the article?

A. To warn us against virus.

B. To remind us the importance of being healthy.

C. To stress the importance of computer.

D. To alert us to economic loss.

Many of the most damaging types of weather begin quickly, strike suddenly, and disappear rapidly, destroying small areas while leaving neighboring areas untouched．Such event as a tornado struck the northeastern part of Edmonton, Alberta, in July 1987．Total damages from the tornado went beyond $250 million, the highest ever for any Canadian storm．

Traditional computer models of the atmosphere have limited value in predicting short-lived local storms like the Edmonton tornado, because the available weather data are generally not detailed enough to allow computers to study carefully the slight atmospheric changes that come before these storms．In most nations, for example, weather-balloon observations are taken just once every twelve hours at places separated by hundreds of miles．With such limited data, traditional forecasting models do a much better job predicting general weather conditions over large areas than they do forecasting specific local events．

Until recently, the observation intensive method needed for exact, very short-range forecasts, or “Nowcasts,” was not possible．The cost of equipping and operating many thousands of conventional weather stations was extremely high, and the difficulties concerned in rapidly collecting and processing the weather data from such a network were hard to overcome．

Fortunately, scientific and technological advances have overcome most of these problems．Radar systems and satellites are all able to make detailed, nearly continuous observation over large areas at a lower cost．Communications satellites can send out data around the world cheaply and immediately, and modern computers can quickly collect and analyze this large amount of weather information．

Meteorologists（气象学者）and computer scientists now work together to design computer programs and video equipment able to change weather data into words and graphic displays that forecasters can understand easily and quickly．As meteorologists have begun using these new technologies in weather forecasting offices, Nowcasting is becoming a reality．

1．Why can’t traditional computer models predict short-lived local storms?

A．The weather data people collect are often wrong．

B．Detailed weather data in some small areas are not available．

C．The computers are not advanced enough to predict them．D．The computers are not used to forecast specific local events．

2．The word “Nowcast” in Paragraph 3 means ________．

A．a network to collect storm data?     

B．a way of collecting weather data

C．a more advanced system of weather observation

D．a forecast which can predict weather in the small area

3．What can make “Nowcasts” a reality according to the passage?

A．Scientific and technological advances． B．Advanced computer programs．

C．Computer scientists．?              D．Meteorologists．

4．What does the passage mainly talk about?

A．The advantages of “Nowcasts”．        B．A tornado in Edmonton, Alberta．

C．The difficulty in predicting tornado．  D．A great development in weather forecast．