Dogs are extremely useful as companions for blind people. When a dog has been properly trained, he will always lead his blind master .in the right direction and keep him out of danger. For example, seeing-eye dogs learn never to cross a busy road when cars are coming, even if their masters command them to do so.

Horses are also able to learn many things too. Horses that are used for guard or police duty must learn never to be frightened of noises, traffic, and other disturbance. Racing horses are able to run much faster than other horses, but they are also quite high strung. Therefore, it is necessary for people who train them to be very patient and understanding.

Pigeons have a natural instinct to return home, even if they are very far away and the trip is hard or dangerous. Men utilize this homing instinct to send messages on small pieces of paper that are fastened to the pigeon’s back or legs. In wartime, pigeons have been known to fly as fast as 75 miles an hour and to cover distances of 500 to 600 miles. These homing pigeons begin their training when they are about four weeks old. After a few weeks they can begin flying and carryingmessages. If all goes well, their flying career lasts about four years.

Animals can learn to do many things that, while not necessarily useful, are very amusing to watch. In circuses, animals are taught to do the tricks that are most compatible with their physical and temperamental make-up. Lions and tigers can be taught to spring gracefully when told to do so, or to stay in place on command. Elephants learn to walk in line, to stand on their hind legs, to lie on their sides, and to stand on their head. They can also learn to dance.

26. a person or animal accompanying someone (Para. 1)

27. give an authoritative order (Para. 1)

28. something that distracts one’s mind (Para. 2)

29. an innate behavior in response to certain stimuli (Para. 3)

30. make practical and effective use of(Para. 3)

31. to continue to function well (Para. 3)

32. entertaining (Para. 4)

33. suitable (Para. 4)

34. jump or make a sudden movement forward (Para. 4)

35. of the back part (Para. 4)

Judging from countless media reports in newspapers from coast to coast, it would surely seem that we have finally got a handle on the Nation’s crime problem. The most recent FBI release of crime statistics for 1995 revealed a welcome drop in violent crime, including an 8 per cent decline in homicide. (46. After four straight years of lower crime levels, some crime experts and law enforcement officials have even dared boldly to suggest that we’re winning the war against crime.)

Though recent trends are encouraging, at least superficially, there is little time to celebrate these successes. It is doubtful that today’s improving crime picture will last for very long. Most likely, this is the calm before the crime storm. (47. While many police officials can legitimately feel gratified about the arrested crime rate — better that it be down than up — there is much more to the great crime drop story.) Hidden beneath the overall drop in homicide and other violent crime is a soaring rate of mayhem among teenagers.

(48. There are actually two crime trends ongoing in America — one for the young and one for the mature, which are moving in opposite directions.) Since 1990, for example, the rate of homicide committed by adults, ages 25 and older, has declined 18 per cent as the baby boomers matured well past their crime prime years. At the same time, however, the homicide rate by teenagers, ages 14 to 17, has increased 22 per cent. Even more alarming and tragic is that over the past decade, the homicide rate at the hands of teenagers has nearly tripled, increasing 172 percent from 1985 to 1994.

Therefore, while the overall U.S. homicide rate has indeed declined in recent years, the rate of juvenile murder continues to grow, unabated by the spread of community policing, increased incarceration, and a variety of other popular crime-fighting strategies. (49. In the overall crime mix, the sharp decline in crime among the large adult population has eclipsed the rising crime rate among the relatively small population of teens.)

Trends in age-specific violent arrest rates for homicide, rape, robbery, and aggravated assault confirm the patterns found in homicide statistics. Teenagers now exceed all age groups, even young adults, in their absolute rate of arrest for violent crime overall. Conventional wisdom in criminology — that young adults generally represent the most violence-prone group—apparently needs to be modified in light of these disturbing changes.

The causes of the surge in youth violence since the mid-1980s reach, of course, well beyond demographics. (50. There have been tremendous changes in the social context of crime over the past decade, which explain why this generation of youth—the young and the ruthless—is more violent than others before it.) Our youngsters have more dangerous drugs in their bodies, more deadly weapons in their hands, and a seemingly more casual attitude about violence. It is clear that too many teenagers in this country, particularly those in urban areas, are plagued with idleness and even hopelessness.

Paragraph Ten

Visitors to Britain are often surprised to find that the weather is an almost endless topic of conversation. This is not because the British are not bright enough to think of anything else to talk about, but because there is always a feature of surprise in the British climate.We never know what is in store for us the next day.

The climatic v______ in Britain.

Paragraph Nine

For thousands of years, people around the world have added special meanings to flowers and plants. In the 1800s flower language reached its height of popularity during the rule of Queen Victoria in England. In the 19th century explorers were bringing back plants from all over the world. A beautiful garden was one way to show a person’s social position and good taste.

Flowers e______ different feelings and emotions.

Paragraph Eight

There’s no easy way to admit this. For years, helpful letter writers told us to stick to science. They pointed out that science and politics don’t mix. They said we should be more balanced in our presentation of such issues as creationism, missile defense and global warming. We resisted their advice and pretended not to be stung by the accusations that the magazine should be renamed Unscientific American, or Scientific Unamerican, or even Unscientific Unamerican.

Readers’ criticism has long been i____ by Scientific American.

Paragraph Five

Some people worry about the violence in TV programs and their effect on young people. Others consider that these same programs are an opportunity for us to release our stronger emotion, our feelings of anger or anxiety. Most people would agree though, that extreme violence should be kept away from children.

Though interpreted differently, most people still agree that children be kept away from v___.

Paragraph Seven

New climate simulations from NASA show that under the warmer global temperatures of the 20th century, water vapor in the atmosphere took longer than normal to fall out of the sky as rain, snow and other precipitation. Generally speaking, the amount decreased over land but increased over oceans.

Warmer weather p____ less rain on land but more at sea.

Paragraph Six

Painters and sculptors create images of the human form; writers tell stories or compose poems about human experience; historians and philosophers ponder the essential qualities of human civilization and nature. And in our own lives, we spend a great deal of our energy and attention on observing our fellow creatures with curiosity and interest.

One of the main preoccupations of the arts and humanities is the o______ of human beings.

Paragraph Three

As we all know, in this rapidly changing world，competition is here and there，especially for high positions.For that reason，it is crucial for those who operate the company or manage the city, town and so on to make decisions，so the work itself needs high quality people to make things better and better.

People should improve themselves to qualify for key positions in politics and b______.

Paragraph Four

Working in more flexible and friendly environments can improve the balance between students，schoolwork and their lives.Not having to commute adds extra time to the day, as much as several hours a week for some students.Thus distance education can also reduce stress，allowing students extra time to study.

Distance education Can improve students’ l______，motivation and interactivity.

Paragraph Two

Quite a number of people believe that women’s abilities are not so good as men’s.As a result，most employers do not choose women to be in charge of important projects.But I think such view is ridiculous.Everyone is born equal and the ability is cultivated later through education，social action and communication.

The prevalent a______ towards working women should be changed.