The findings come ___36___ a study of nearly 1,000 US people that looked at diet, calorie intake and body mass index (BMI) - a measure of obesity.___37___ is found that those who ate chocolate a few times a week were, on ___38___, slimmer than those ___39___ ate it occasionally. Even though chocolate is loaded with calories, it contains ingredients（材料）that may favour weight loss ___40___ than fat synthesis, scientists believe.___41___ boosting calorie intake, regular chocolate consumption was related to lower BMI in the study, ___42___ is published in Archives of Internal Medicine. The link remained even when other factors, like how ___43___ exercise individuals did, were taken into ___44___.And it appears it is how often you eat chocolate that is important, rather than how much of it you eat. The ___45___ found no link with quantity consumed.

___46___ to the researchers, there is only one chance in a hundred that their findings could be explained by chance alone. Lead author Dr Beatrice Golomb, from the University of California at San Diego, said: "Our findings appear to add to a body of information suggesting that the composition of calories, not just the number of them, matters for determining their ultimate impact on weight."This is not the first time scientists ___47___ that chocolate may be healthy for us. Other studies have claimed chocolate may be good for the heart. Consumption of certain types of chocolate has been linked to some favourable changes in blood pressure, insulin（胰岛素）sensitivity and cholesterol（胆固醇）level. And chocolate, ___48___ dark chocolate, does contain antioxidants（抗氧化剂）which can help to mop up harmful free radicals - unstable chemicals that can damage our cells.

Dr Golomb and her team believe that antioxidant compounds, called catechins（儿茶素）, can improve lean muscle mass and reduce weight  ___49___ studies in rodents would suggest this might be so. Mice ___50___ for 15 days with epicatechin (present in dark chocolate) had improved exercise performance and observable changes to their muscle composition.They say clinical trials are now needed in humans to see ___51___ this is the case.

But before you reach ___52___ a chocolate bar, there are still lots of unanswered questions. And in the absence of conclusive evidence, experts advise caution.While there's no harm in allowing yourself a treat like ___53___ now and again, eating too much might be harmful because it often ___54___ a lot of sugar and fat too.And if you are looking to change your diet, you are ___55___ to benefit most from eating more fresh fruits and vegetables.

 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.”
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