C

  Things similar continuously happened in Haiti and Chile．Thousands of people were

buried in the earthquake and lost their fives．What if we could have warned them? People are always trying hard to find a way of preventing building collapsing(坍塌)．Better materials and technology help，but are not a solution．Just like humans，a building has its own life circle from  “birth” to “death”．If we know when a building is going to collapse，we can repair it in advance or get out before it falls．

    Now, scientists at the University of Illinois ha、，e developed a material that turns red before it breaks．The invention could be used in things like climbing ropes，or bridge supports．The secret behind the color-changing material is a type of molecule(分子)．A molecule is a group of atoms held together by chemical bonds(化学键)．Imagine you and your friends standing in a circle，holding hands．Each person stands for one atom，your hands represent the bonds，and the entire circle represents a molecule．If one person lets go of his or her hands，the molecule changes color．The research team put the molecule into a soft material．When the researchers stretched(拉长) the material：it turned bright red a few seconds before it broke into two pieces．

When they repeatedly stretched and relaxed the material，without breaking it，it only turned a little red．

The major problem is，light can get rid of the red color．When the team shone a bright light on the molecule，the broken bond was fixed，and the color disappeared．If bright fight keeps the red color from appearing，the material’s warning system will be useless．Scientists still have a lot of work to do before the color-changing molecule can be used outside the lab．

49.The passage is mainly about______________

A．a way of preventing building from breaking down

B．a series'-of earthquakes in Haiti and Chile

C．a way of warning before buildings collapse

D．a newly—discovered structure of a molecule

50.According to the passage，we call conclude that____________

A．there are problems to solve before putting the new material to use

B．scientists have found the life circle of buildings from “birth” to “death”

C．bright fight makes the red color visible to human eyes

D．the new material is unlikely to be used in building bridges

51.The color-changing molecule can___________

A．make building materials much stronger

B．help building materials get stretched if necessary

C．prevent the earthquake from killing people

D．remind people to leave buildings before they fall

52．The warning system is based on the fact that____________

A．red color won’t show up when it meets bright fight

B．a material with a certain type of molecule Can turn red when setched

C．a building has its own life circle of “birth”to“death”

D．the broken bond will fix itself when a molecule meets bright fight

  Things similar continuously happened in Haiti and Chile．Thousands of people were

buried in the earthquake and lost their fives．What if we could have warned them? People are always trying hard to find a way of preventing building collapsing(坍塌)．Better materials and technology help，but are not a solution．Just like humans，a building has its own life circle from  “birth” to “death”．If we know when a building is going to collapse，we can repair it in advance or get out before it falls．

    Now, scientists at the University of Illinois ha、，e developed a material that turns red before it breaks．The invention could be used in things like climbing ropes，or bridge supports．The secret behind the color-changing material is a type of molecule(分子)．A molecule is a group of atoms held together by chemical bonds(化学键)．Imagine you and your friends standing in a circle，holding hands．Each person stands for one atom，your hands represent the bonds，and the entire circle represents a molecule．If one person lets go of his or her hands，the molecule changes color．The research team put the molecule into a soft material．When the researchers stretched(拉长) the material：it turned bright red a few seconds before it broke into two pieces．

When they repeatedly stretched and relaxed the material，without breaking it，it only turned a little red．

The major problem is，light can get rid of the red color．When the team shone a bright light on the molecule，the broken bond was fixed，and the color disappeared．If bright fight keeps the red color from appearing，the material’s warning system will be useless．Scientists still have a lot of work to do before the color-changing molecule can be used outside the lab．

49. The passage mainly about

A. a way of preventing building from breaking down

B. a series of earthquakes in Haiti and Chile

C. a way of warning before buildings collage

D. a newly-discovered structure of a molecule

50．According to the passage，we call conclude that

A．there are problems to solve before putting the new material to use

B．scientists have found the life circle of buildings from “birth” to “death”

C．bright fight makes the red color visible to human eyes

D．the new material is unlikely to be used in building bridges

51．The color-changing molecule can

A．make building materials much stronger

B．help building materials get stretched if necessary

C．prevent the earthquake from killing people

D．remind people to leave buildings before they fall

52．The warning system is based on the fact that

A．red color won’t show up when it meets bright fight

B．a material with a certain type of molecule Can turn red when s廿etched

C．a building has its own life circle of “birth”to“death”

D．the broken bond will fix itself when a molecule meets bright fight

Europe’s deadly outbreak of a rare form of E. coli bacteria (大肠杆菌) has brought new attention to food safety issues. One of the problems when people get sick from food is that the simplest question is often difficult or even impossible to answer. Just what did the people eat that made them sick?
Of course, one way to avoid these medical mysteries is to keep dangerous organisms out of the food supply. This is easier said than done, but scientists keep looking for new ways.
Scientists in the United States have developed an experimental system that uses a high-tech optical scanner. The system is designed to identify the presence of contaminants(致污物) like soil or animal waste on fresh produce. These can be sources of E. coli. E. coli bacteria naturally live in the intestines(肠) of humans and many animals. Most kinds of E. coli are harmless but some can make people sick.
The new scanner can also show damage and imperfections that might make the produce unappealing to shoppers.
Scientists designed the system at a Department of Agriculture research center in Beltsville, Maryland. Moon Kim of the Agricultural Research Service led the team.
MOON KIM: “We were requested, we were asked, to develop a method to detect contamination in produce. So we started with the apple as the model sample.”
The scanner uses a high-speed camera placed over the conveyer belt that moves the produce along. As the apples move along the belt, the scanner captures images of each piece of fruit.
Moon Kim says the team hopes the system will be available before long.
MOON KIM: “We are targeting for development in commercial plants for the next several years.”
The scanner can direct a sorting machine to separate the bad apples from the good ones. The system is currently able to show the surface of only half the apple as it speeds by. The inventers hope to improve the process so it can show the whole surface.
1.What is the main topic of the text?

A．Bacteria.?? B．A high-tech scanner.

C．A camera??? D．Food safety.

2.E. coli bacteria ______.

A．broke out all over the world????????????? B．comes from soil or animal waste

C．is extremely harmful to health????????????? D．does not cause illness

3.The high-tech scanner ______.

A．can help to sort out different fruits

B．make the produce appeal to shoppers

C．can only capture images of the whole apple

D．can identify the presence of contaminants

4.What can be inferred from the text?

A．The scanner needs to be improved.

B．The scanner will be available in the next several years.

C．Moon Kim is unwilling to develop the scanner.

D．The scanner is connected to a sorting machine.

 “Well, what did I say？Buck’s a real fighter, all right,” said Francois the next morning when he discovered that Spitz had disappeared and that Buck was covered in blood．

“Spitz fought like a wolf,” said Perrault, as he looked at the bites all over Buck．

“And Buck fought like ten wolves,” answered Francois. “And we'll travel faster now. No more Spitz，no more trouble.”

Francois started to harness the dogs. He needed a new lead-dog, and decided that Solleks was the best dog that he had. But Buck jumped at Solleks and took his place．

“Look at Buck！” said Francois，laughing. “He's killed Spitz，and now he wants to be lead-dog．Go away, Buck！”

He pulled Buck away and tried to harness Solleks again．Solleks was unhappy too. He was frightened of Buck, and when Francois turned his back，Buck took Solleks’ place again. Now Francois was angry．

“I'll show you! ” he cried，and went to get a heavy club from the sledge．

Buck remembered the man in the red coat，and moved away. This time，when Solleks was harnessed as lead-dog，Buck did not try to move in．He kept a few meters away and circled around Francois carefully. But when Francois called him to his old place in front of Dave, Buck refused．He had won his fight with Spitz and he wanted to be lead－dog．

For an hour the two men tried to harness him．Buck did not run away，but he did not let them catch him．Finally，Francois sat down，and Perrault looked at his watch．It was getting late. The two men looked at one another and smiled. Francois walked up to Solleks，took off his harness， led him back and harnessed him in his old place．Then he called Buck. All the other dogs were harnessed and the only empty place was now the one at the front. But Buck did not move．

“Put down the club,” said Perrault．

Francois dropped the club, and immediately Buck came up to the front of the team．Francois harnessed him, and in a minute the sledge was moving．

Buck was an excellent leader. He moved and thought quickly and led the other dogs well. A new leader made no difference to Dave and Solleks; they continued to pull hard．But the other dogs had had an easy life when Spitz was leading．They were surprised when Buck made them work hard and punished them for their mistakes. Pike，the second dog，was usually lazy；but by the end of the first day he was pulling harder than he had ever pulled in his life. The first night in camp Buck fought Joe，another difficult dog，and after that there were no more problems with him．The team started to pull together，and to move faster and faster．

“I've never seen a dog like Buck!” cried Francois, “Never! He's worth a thousand dollars. What do you think, Perrault? ”

Perrault agreed．They were moving quickly，and covering more ground every day. The snow was good and hard，and no new snow fell．The temperature dropped to 45°C below zero, and didn't change．

This time there was more ice on the Thirty Mile River, and they crossed in a day．Some days they ran a hundred kilometers，or even more. They reached Skagway in fourteen days; the fastest time ever．

1.The writer mentioned “the man in the red coat” in the passage to show that____.

A．the man in the red coat once beat Buck severely with a club.

B．Buck remembered Francois was the man in the red coat.

C．the man in the red was quite friendly to Buck in his memory.

D．Buck remembered Francois was a friend of the man in the red coat.

2. Why did Buck fight Joe the first night in camp?

A．He wanted to get rid of Joe.

B．He wanted to make some trouble.

C．He was interested in fighting with others.

D．He wanted to teach Joe a lesson.

3. According to the passage, which of the following is true about the other dogs?

A．Dave stood in the second position in the team.

B．Joe was always quite lazy in the team.

C．Pike was a trouble-maker in the team.

D．Solleks was hard-working in the team.

4. What did Francois think of Buck at the end of the passage?

A．annoying          B．admirable         C．aggressive         D．average

5. Which of the following best shows that Buck was an excellent leader?

A．He killed Spitz at the beginning of the story.

B．He punished them for their mistakes.

C．He fought Joe the first night in camp.

D．They reached Skagway in the fastest time ever.

6.Which of the following is the best title for the passage?

A．The Fight with Dogs B．The New Lead-dog   C．A Dog Called Buck   D．A Real Fighter

 "The world's oceans are slowly getting more acidic,”say scientists. The researchers from California report that the change is taking place in response to higher levels of carbon dioxide in the atmosphere.

    The lowering of the waters’pH value is not great at the moment but could cause a serious threat to current ocean life if it continues, they warn. Ken Caldeira and Michael Wickett, from the Lawrence Livermore National Laboratory, report their concerns in the journal Nature.

Increasing use of oil fuels means more carbon dioxide is going into the air, and most of it will eventually be absorbed by seawater. Once in the water, it reacts to form carbonic acid. Scientists believe that the oceans have already become slightly more acidic over the last century.

    These researchers have tried to predict what will happen in the future by combining what we know about the history of the oceans with computer models of climate change．"This level of acidity will get much more extreme in the future if we continue releasing CO2 into the atmosphere," said Dr Caldeira. "And we predict the amount of future acidity will exceed（超过）anything we have seen over the last several hundred million years, let alone perhaps after rare disastrous events such as asteroid（小行星) impacts．”

    However, it is not absolutely clear what that means for ocean life．Most organisms live near the surface, where the greatest pH change would be expected to occur, but deep-ocean life forms may be more sensitive to pH changes．Coral reefs and other organisms whose shells contain calcium carbonate（小行星) may be particularly affected if the water's acidity levels keep going up, the team predict. They could find it much more difficult to build these structures in water with a lower pH.

    In recent years some people have suggested storing carbon dioxide from power stations in the deep ocean as a way of dealing with global warming．But Dr Caldeira said that such a strategy should now be re-considered. "Previously, most experts had looked at ocean absorption of carbon dioxide as a good thing-because in releasing CO2 into the atmosphere we warm the planet, and when CO2, is absorbed by the ocean, it reduces the amount of greenhouse warming.”

According to Dr Caldeira,__________ .

   A. ocean absorption of carbon dioxide is a good thing

   B. more oil fuels will be used in the near future

   C. scientists may predict climate changes with computer models

   D. the future situation of the amount of acidity is extremely serious

f the water's acidity level keeps rising,_________ .

   A. ocean life whose structures contain calcium carbonate may be affected

   B. the waters’pH value will become higher and higher

   C. organisms living near the surface are more sensitive to pH changes

   D. some disastrous events will occur more often than before

Most experts once believed storing carbon dioxide in the ocean would reduce________ .

   A. the CO2 absorbed by the ocean             B. the amount of greenhouse warming

   C. the acidity of the ocean                   D. the gradual release of CO2

The purpose of this passage is to_________ .

   A. show people the findings of a research team   B. inform people of how acid the ocean is now

   C. introduce Dr Caldeira and his team's research  D. warn people of the higher level of CO2