When people first walked across the Bering Land Bridge thousands of years ago, dogs were by their sides, according to a study published in the journal Science.

When people first walked across the Bering Land Bridge thousands of years ago, dogs were by their sides, according to a study published in the journal Science.

　 Robert Wayne of the University of California, Los Angeles, and Jennifer Leonard of the Smithsonian Institute, used DNA material—some of it unearthed by miners in Alaska—to conclude that today’s domestic dog originated in Asia and accompanied the first humans to the New World about 10,000 to 15,000 years ago. Wayne suggests that man’s best friend may have enabled the tough journey from Asia into North America. “Dogs may have been the reason people made it across the land bridge,” said Wayne. “They can pull things, carry things, defend you from fierce animals, and they’re useful to eat.”

　 Dog remains from a Fairbanks-area gold mine helped the scientists reach their conclusion. Leonard, an evolutionary biologist, collected DNA from 11 bones of ancient dogs that were locked in permafrost(永冻层) until Fairbanks miners uncovered them in the 1920s. The miners donated the preserved bones to the American Museum of Natural History in New York City, where they remained untouched for more than 70 years. After borrowing the bones from the museum, Leonard and her colleagues used radiocarbon techniques to find the age of the Alaska dogs. They found the dogs all lived between the years of 1450 and 1675 A.D., before Vitus Bering and Aleksey Chirikov who were the first known Europeans to view Alaska in 1741. The bones of dogs that wandered the Fairbanks area centuries ago should therefore be the remains of “pure native American dogs,” Leonard said. The DNA of the Fairbanks dogs would also expose whether they were the descendents of wolves from North America.

　 Leonard and Wayne’s study suggests that dogs joined the first humans that made the adventure across the Bering Land Bridge to slowly populate the Americas. Wayne thinks the dogs that made the trip must have provided some excellent service to their human companions or they would not have been brought along. “Dogs must have been useful because they were expensive to keep,” Wayne said. “They didn’t feed on mice; they fed on meat, which was a very guarded resource.”

68. The first humans into the New World brought dogs along with them because dogs　　　　 .

　 A. kept people company B. were easy to stay alive

C. helped protect the supplies D. offered excellent service

69. The underlined word “remains” in Paragraph 3 probably refers to 　　　　　.

　 A. dead bodies B. animal waste　　 　 C. leftover food　 　　 D. living environment

70. According to the study described in Paragraph 3, we can learn that 　　　　　.

　 A. ancient dogs entered North America between 1450 and 1675 AD

　 B. the 11 bones of ancient dogs are not from native American dogs

　 C. the bones studied were not from dogs brought by Europeans

D. the bones found by the gold miners were from American wolves

71. The passage mainly talks about 　　　　　.

　 A. the DNA study of dogs in NorthAmerica 　

B. the origin of the North American dogs

C. why ancient people brought dogs to America 　

D. the difference between Asian and American dogs

When people first walked across the Bering Land Bridge thousands of years ago, dogs were by their sides, according to a study published in the journal Science.
Robert Wayne of the University of California, Los Angeles, and Jennifer Leonard of the Smithsonian Institute, used DNA material—some of it unearthed by miners in Alaska—to conclude that today’s domestic dog originated in Asia and accompanied the first humans to the New World about 10,000 to 15,000 years ago. Wayne suggests that man’s best friend may have enabled the tough journey from Asia into North America. “Dogs may have been the reason people made it across the land bridge,” said Wayne. “They can pull things, carry things, defend you from fierce animals, and they’re useful to eat.”
Researchers have agreed that today’s dog is the result of the domestication(驯化) of wolves thousands of years ago. Before this recent study, a common thought about the precise origin of North America’s domestic dog was that Natives domesticated local wolves, the descendents(后代) of which now live with people in Alaska, Canada, and the Lower 48.
Dog remains from a Fairbanks-area gold mine helped the scientists reach their conclusion. Leonard, an evolutionary biologist, collected DNA from 11 bones of ancient dogs that were locked in permafrost(永冻层) until Fairbanks miners uncovered them in the 1920s. The miners donated the preserved bones to the American Museum of Natural History in New York City, where they remained untouched for more than 70 years. After borrowing the bones from the museum, Leonard and her colleagues used radiocarbon techniques to find the age of the Alaska dogs. They found the dogs all lived between the years of 1450 and 1675 A.D., before Vitus Bering and Aleksey Chirikov who were the first known Europeans to view Alaska in 1741. The bones of dogs that wandered the Fairbanks area centuries ago should therefore be the remains of “pure native American dogs,” Leonard said. The DNA of the Fairbanks dogs would also expose whether they were the descendents of wolves from North America.
Along with the Fairbanks samples, the researchers collected DNA from bones of 37 dog specimens(标本) from Mexico, Peru, and Bolivia that existed before the arrival of Columbus. In the case of both the Alaska dogs and the dogs from Latin America, the researchers found that they shared the most genetic material with gray wolves of Europe and Asia. This supports the idea of domestic dogs entering the New World with the first human explorers who wandered east over the land bridge.
Leonard and Wayne’s study suggests that dogs joined the first humans that made the adventure across the Bering Land Bridge to slowly populate the Americas. Wayne thinks the dogs that made the trip must have provided some excellent service to their human companions or they would not have been brought along. “Dogs must have been useful because they were expensive to keep,” Wayne said. “They didn’t feed on mice; they fed on meat, which was a very guarded resource.”

1. 1.

   The underlined word “remains” is closed in meaning to ______

   1. A.
      leftover food
   2. B.
      animal waste
   3. C.
      dead bodies
   4. D.
      living environment
2. 2.

   According to the study described in Paragraph 4, we can learn that ______

   1. A.
      ancient dogs entered North America between 1450 and 1675 AD
   2. B.
      the 11 bones of ancient dogs are not from native American dogs
   3. C.
      the bones discovered by the gold miners were from North American wolves
   4. D.
      the bones studied were not from dogs brought into North America by Europeans
3. 3.

   What can we know from the passage?

   1. A.
      Native Americans domesticated local wolves into dogs
   2. B.
      Scientists discovered some ancient dog remains in 1920s
   3. C.
      Latin America’s dogs are different from North America’s in genes
   4. D.
      Ancient dogs entered North America across the Bering Land Bridge
4. 4.

   The first humans into the New World brought dogs along with them because ______

   1. A.
      dogs fed on mice
   2. B.
      dogs were easy to keep
   3. C.
      dogs helped protect their resources
   4. D.
      dogs could provide excellent service
5. 5.

   What does the passage mainly talk about ______

   1. A.
      the origin of the North American dogs
   2. B.
      the DNA study of ancient dogs in America
   3. C.
      the reasons why early people entered America
   4. D.
      the difference between Asian and American dogs

Grown-ups know that people and objects are solid. At the movies, we know that if we reach out to touch Tom Cruise, all we will feel is air. But does a baby have this understanding?

To see whether babies know objects are solid. T. Bower designed a method for projecting an optical illusion(视觉影像)of a hanging ball. His plan was to first give babies a real ball, one they could be expected to show surprised in their faces and movements, All the 16 to 24-week-old babies tested were surprised when they reached for the illusion and found that the ball was not there.

Grown-ups also have a sense of object permanence. We know that if we put a box in a room and lock the door, the box will still be there when we come back. But does a baby realize that a ball that rolls under a chair does not disappear and go to never-never land?

Experiments done by Bower suggest that babies develop a sense of object permanence when they are about 18 weeks old. In his experiments, Bower used a toy train that went behind a screen. When 16-week-old and 22-week-old babies watched the toy train disappear behind the left side of the screen, they looked to the right, expecting it to re-appear. If the experiment took the train off the table and lifted the screen, all the babies seemed surprised not to see the train. This seems to show that all the babies had a sense of object permanence. But the second part of the experiment showed that this was not really the case. The re-searcher substituted(替换) a ball for the train when it went behind the screen. The 22-week-old babies seemed surprised and looked back to the left side for the train. But the 16-week-old babies did not seem to notice the switch(更换).Thus,the 16-week-old babies seemed to have a sense of “something permanence,” while the 22-week-old babies had a sense of object permanence related to a particular object.

1.The passage is mainly about        .

A.babies’sense of sight                   B.effects of experiments on babies

C.babies’understanding of objects          D.different tests on babies’feelings

2..In Paragraph 3, “object permanence” means that when out of sight, and object           .

A.still exists        B.keeps its shape           C.still stays solid      D.is beyond reach

3..What did Bower use in his experiments?

A.A chair         B.A screen              C.A film            D.A box

4.. Which of the following statements is TRUE?

A.The babies didn’t have a sense of direction.

B.The older babies preferred toy trains to balls.

C. The younger babies liked looking for missing objects

D.The babies couldn’t tell a ball from its optical illusion.

Here is some news of the future.

March 20, 2035

There was a lot of news around the life extension drugs that hit the market a decade ago. They didn't promise that you would like forever, but they gave you a chance to extend your life an extra five to ten years. Even though the life expectancy rate at birth has increased greatly, the life expectancy for seniors hasn't improved that much. Basically, you have a greater chance to become a senior, but you will not have a much longer lifespan, and this is where the anti-aging drugs intend to kick in. So, do the anti-aging drugs work? Well，it is too early to tell. But the sales so far are very good.

April 19, 2035

Of the total US population of 378 million, people over 65 years of age now make up 20% for the first time. The senior ratio of only 4.1% by year 1900, and 12.4% 30 years ago.

The number of people above 65 compared to those of what is considered working ages, between 15 and 64, is currently 33.7%. This is up from 18.5% since year 2005, which means that for every retired person there are now two workers, compared to four workers 30 years ago. The number of people above the age of 80 has grown to 23.8 million, making them 6.3% of the total population compared to 3.6% in 2005.

April 12, 2040

Although introduced in the market only five years ago, 10% of all hydrogen fuel now sold in the US is of the environmentally friendly Re-Hydro label, produced through eletrolysis(电解) based on a source of 100% renewable energy. Several producers have turned to producing Re-Hydro, mainly because of lower tax, which also keeps the price of Re-Hydro on the same level as regular hydrogen. Most analysts believe that Re-Hydro will be the dominating fuel in the future.

1.According to News 1 we know that the life extension drugs ____.

A．were first sold in the year 2025.

B．are made to make people live forever.

C．should be taken when people are young.

D．have greatly increased the life expectancy rate at birth.

2.The sales of the life extension drugs so far clearly show that_____.

A．people have no faith in them

B．people want to give them a try

C．they work very well for seniors

D．they have no effect on people’s health

3.What can we learn from News 2?

A．Many Americans will find it hard to find a job.

B．It’s very hard for seniors to pass the age of 80.

C．The US population has been increasing rapidly since 2005.

D．The US population has been aging rapidly since 2005.

4.We can know from the passage that the fuel of the Re-Hydro label is ______.

A．expensive         B．cheap            C．green            D．dangerous

5.What can we infer from News 3?

A．Re-Hydro will be widely used in the future.

B．The government discourages the production of Re-Hydro.

C．Producers are not interested in producing Re-Hydro.

D．Re-Hydro is more expensive than regular hydrogen.