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Thousands of years (21) humans began the process of domesticating the dog and shaping what "being a dog" really means. Through careful selection and breeding, an astonishing variety of dog breeds (22) been created. Desirable traits have been selected for in various breeds that are of a benefit (23) humans. There are some traits, however, that quickly become undesirable when expressed too frequently. Barking is a(an) (24) of a natural behavior that is encouraged in terms of guarding behavior, but becomes a problem when the behavior is produced in excess. A recent health insurance investigation revealed (25) the sound of a continually barking dog was cited as the most disruptive and stress inducing (26) for humans.
Barking, in addition to whining, howling and growling, is a dog’s (27) means of communication. Barking is characterized by a series of short, sharp sounds, that tend to vary (28) <
A. you 
B. one 
C. dogs 
D. we

[单项选择]Man’s story in China began many thousands of years ago. Remains of an early form of man discovered in China, known as Peking Man, indicate that Stone Age men lived in the area as long as 500,000 years ago. During the centuries that followed, their descendants laid the foundations of civilization in China.
Throughout its history, China has been a rich source of inventions. Silk, the compass, tea and porcelain originated there. In addition, they are responsible for the invention of paper and printing. The Chinese had used ink as early as 1200 B.C., an excellent type which they made from lampblack and which is known in English as India ink or China ink. By the end of the first century A.D., the Chinese had invented paper.
The Chinese also invented printing. Early Chinese printing is called block printing. The printer carved raised characters on a block of wood, wet the surface of the characters with ink, and pressed sheets of paper against them. Printers in the l
A. foreigners
B. following generations
C. enemies
D. fossilized remains

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Gap years began because Oxford and Cambridge
A. demanded all students take one.
B. demand all students take one.
C. only considered applicants whose results were known.
D. only consider applicants whose results are known.

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Most of us walk and carry items in our hands every day. These are seemingly simple activities that the majority of us don’t question. But an international team of researchers, including Dr. Richmond from GW’s Columbian College of Arts and Sciences, have discovered that human walking upright, may have originated millions of years ago as an adaptation to carrying scarce, high-quality resources. The team of researchers from the US, England, Japan and Portugal investigated the behavior of modern-day chimpanzees as they competed for food resources, in an effort to understand what ecological settings would lead a large ape—one that resembles the 6 million-year old ancestor we shared in common with living chimpanzees—to walk on two legs.
"These chimpanzees provide a model of the ecological conditions under which our earliest ancestors might ha
A. regarded both types of nut as priced resources
B. preferred oil palm nuts to coula nuts
C. liked coula nuts better than oil palm nuts
D. ignored both types of nut altogether