Many studies have shown that the company of pets can help lower blood pressure and raise chances of recovering from a heart attack, reduce loneliness and help control body weight.

Any pet owner will tell you how much joy a pet brings. For some, an animal provides more comfort than a husband/wife. A 2002 study by Karen Allen of the State University of New York measured stress levels and blood pressure in people (half of them were pet owners) while they performed 5 minutes of mental arithmetic (算术) or held a hand in ice water. People completed the tasks alone, with a husband/wife, a close friend or with a pet. People with pets did it best. Those tested with their animal friends had smaller change in blood pressure and returned most quickly to baseline heart rates. With pets in the room, people also made fewer math mistakes than when doing in front of other companions. It seems that people feel more relaxed around pets, says Allen, who thinks it may be because pets don’t judge.

   A study reported last fall suggests that having a pet dog may also have an effect on your body weight. Researchers at Northwestern Memorial Hospital spent a year studying two groups of fat people who were put on a diet-and-exercise program: one group with pet dogs, and the other without. On average, dog owners lost about 11 pounds, or 5% of their body weight; While those without dogs lost about 8 pounds. The pet owners, said researchers, got more exercise overall (mostly with their dogs) and found it worth doing.

C

      Delicate step gives mosquitoes strength to walk on water.

   It's not a magical power. Mosquitoes can walk on water because of the angle at which their legs touch its surface.

   A mosquito's leg is strong enough to bear up to 23 times its total body weight, which is one reason why it can walk on water so effortlessly. This is far greater than the leg strength of other water-walking insects like water striders(水黾), whose legs have been more carefully studied.

   Jian-Lin Liu of the China University of Petroleum in Qingdao and his colleagues thought a mosquito's advantage might also come from the protective wax and microscopic scales(鳞片) coating its legs. They removed these layers(层) and measured the change in the leg's load-bearing capacity(承重能力), but found that the layers were responsible for less than 12.5 percent of the overall supporting force.

   The main player turned out to be the angle between the leg and the water surface. The supporting force was strongest when the leg was nearly parallel to the surface. Any angle greater than 62 degrees would make the mosquito fall through the surface.

The researchers believe that mosquitoes can adjust this angle during landing and take-off to ensure they remain on the water's surface. This ability is very important because many species land on fresh or still water to lay their eggs in it.

    The work could inspire insect-like robots and waterproof materials, the team says.

     How to deal with waste has been a problem since humans started producing it. As more and more people choose to live close together in cities, the waste-disposal（处理）problem becomes increasingly difficult.

       During the eighteenth century, it was usual for several neighboring towns to get together to select a faraway spot as a dump site. Residents or trash haulers（垃圾拖运者）would transport household rubbish, rotted wood, and old possessions to the site. Periodically（定期地）some of the trash was burned and the rest was buried. The unpleasant sights and smells caused no problem because nobody lived close by.
           Factories, mills, and other industrial sites also had waste to be disposed of. Those located on rivers often just dumped the unwanted remains into the water. Others built huge burners with chimneys to deal with the problem.

        Several facts make these choices unacceptable to modern society. The first problem is space.  Landfills(填埋场)are most needed in heavily populated areas. Such areas rarely have empty land suitable for this purpose. Property is either too expensive or too close to residential（住宅区的）neighborhoods. Long-distance trash hauling has been a common practice, but once farm areas are refusing to accept rubbish from elsewhere, cheap land within trucking distance of major city areas is almost nonexistent.

      Awareness（意识）of pollution dangers has led to more strict rules of waste disposal. Pollution of rivers, ground water, land and air is a price people can no longer pay to get rid of waste. The amount of waste, however, continues to grow.

       Recycling efforts have become commonplace, and many towns require their people to take part. However, even the most efficient recycling programs can hope to deal with only about 50 percent of a city’s reusable waste.

C

Light travels at a speed which is about a million times faster than the speed of sound. In one second, light travels about 300,000km, but sound travels only 344m. You can get some idea of this difference by watching the start of a race. If you stand some distance away from the starter, you can see smoke come from his gun before the sound reaches your ears. This great speed of light produces some strange facts.   Sunlight takes about 8 minutes to reach us. If you look at the light of the moon tonight,   remember that the light rays（光线）left the moon 1.3 seconds before they reached you.

The nearest star is so far away that the light which you can see from it tonight started to travel towards you four years ago at a speed of nearly 2 million km per minute. In some cases(在某种情况下) the light from one of tonight’s stars started on its journey to you before you were born.
   Thus, if we want to be honest, we cannot say “ The stars are shining tonight.” We have to say, “ The stars look pretty. They were shining four years ago but their light has only just reached Earth.”

Using too much water or throwing rubbish into our rivers are clear ways that humans can put our water supply in danger, but we also affect our water supply in less obvious ways. You may wonder how paving(铺砌) a road can lead to less useable fresh water. A major part of the  water we use every day is groundwater. Groundwater does not come from lakes or rivers.It comes from underground. The more roads and parking lots we pave, the less water can flow into the ground to become groundwater.

    Human activity is not responsible for all water shortages. Drier climates are of course more likely to have droughts than areas with more rainfall，but in any case, good management can help to make sure there is enough water to meet our basic needs.

    Thinking about the way we use water every day can make a big difference, too. In the United States, a family of four can use 1.5 tons of water a day! This shows how much we depend on water to live，but there's a lot we can do to lower the number.

You can take steps to save water in your home.To start with, use the same glass for your drinking water all day. Wash it only once a day. Run your dishwasher only when it is full. Help your parents fix any leaks in your home. You can even help to keep our water supply clean by recycling batteries instead of throwing them away.

       Stonehenge may have been a prehistoric health center rather than a site for observing stars or a temple in honor of the dead, scientists said yesterday. New evidence unearthed at the World Heritage Site in more than 40 years suggests that the monument was a place where the diseased and injured went in groups, seeking cures.

      After a two-week dig, scientists have concluded that Stonehenge was “the ancient healthcare centre of southern England” because of the existence of “bluestones”---the smaller columns of dolerite that formed an earlier stone structure.

      By dating pieces of remains to around 7330BC, Tim Darvill, of Bournemouth University, and Goff Wainwright, of the Society of Antiquaries have found that hunter-gatherers were at the site on Salisbury Plain 4,000 years earlier than thought. The first stage of Stonehenge, a round earthwork structure, was built around 3000BC. Professor Wainwright added: “I did not expect the degree of complexity we discovered. We’re able to say so much more about when Stonehenge was built and why---all of which changes our previous understanding of the monument.”

      The research reveals the importance of the henge’s famous bluestones. Hundreds of bluestone chips gathered at the site have led the team to conclude that the bluestones were valued for their curing effects---the key reason that about 80 of them, each weighing up to 4 tons and a half, were dragged more than 150 miles from the Preseli Hills to Wiltshire. After years of research, Professors Darvill and Wainwright have concluded that, for thousands of years, the Preseli mountain range was home to magical health centers and holy wells.

      Even today there are those who believe in the curing powers of the springs for coughs and heart disease, and people who use crystals and bluestones for self-curing. Radiocarbon tests have also revealed that the construction of the original bluestone circle took place around 2300BC, three centuries later than originally thought. Interestingly, on the same day died the “Amesbury Archer”---a sick traveler from the Swiss or German Alps who had an infected knee---whose remains were discovered about five miles from Stonehenge. The professors believe that he was a devoted religious person who was hoping to benefit from the curing powers of the monument.

       An English saying goes: “All work and no play makes Jack a dull boy.” That means we should relax after a day’s hard work or we’ll be unhealthy.

       Many students know that if they want to get ideal jobs with good salaries, they must do well in high school so they can enter good universities. Therefore, they spend all day studying without time to relax.

       However, not all students can go to top universities even if they work very hard. Students are pressurized by parents and teachers who are just concerned about their studies and exam scores while ignoring their hobbies and individual differences. As a result, students are forces to work harder and harder. Furthermore, there is pressure coming from students themselves. They realize they have a slim chance of getting into a top university as competition is fierce. So, they put a lot of stress on themselves and stay in a nervous state day after day. If they keep it up,   they’ll suffer illnesses; both psychological and physical.

       What students need is relaxation. This doesn’t mean that they should give up their ambitions and stop studying hard. It means “work while you work, play while you play”. If you can do this, you will improve your health greatly. You’ll feel yourself suddenly fresh, just like recovering from a terrible illness. You’ll find that your studies are not a burden(负担) anymore.

C

How could we possibly think that keeping animals in cages in unnatural environments－mostly for entertainment purposes－is fair and respectful?
    Zoo officials say they are concerned about animals. However, most zoos remain “collections” of interesting “things” rather than protective habitats. Zoos teach people that it is acceptable to keep animals bored, lonely, and far from their natural homes.
    Zoos claim to educate people and save endangered species, but visitors leave zoos without having learned anything meaningful about the animals’ natural behavior, intelligence, or beauty. Zoos keep animals in small spaces or cages, and most signs only mention the species’ name, diet, and natural range. The animals’ normal behavior is seldom noticed because zoos don’t usually take care of the animals’ natural needs.
    The animals are kept together in small spaces, with no privacy and little opportunity for mental and physical exercise. This results in unusually and self-destructive behavior called zoochosis. A worldwide study of zoos found that zoochosis is common among animals kept in small spaces or cages. Another study showed that elephants spend 22 percent of their time making repeated head movements or biting cage bars, and bears spend 30 percent of their time walking back and forth, a sign of unhappiness and pain.
    Furthermore, most animals in zoos are not endangered．Captive breeding(圈养繁殖) of endangered big cats, Asian elephants, and other species has not resulted in their being sent back to the wild．Zoos talk a lot about their captive breeding programs because they do not want people to worry about a species dying out. In fact, baby animals also attract a lot of paying customers. Haven’t we seen enough competitions to name baby animals?
    Actually, we will save endangered species only if we save their habitats and put an end to the reasons people kill them. Instead of supporting zoos, we should support groups that work to protect animals’ natural habitats.

A child ties one end of a string to a stick and the other end around the "neck" of an insect. Holding the stick, the child lets the insect go. With a loud whirring sound, the insect takes off, pulling the string in a large curve over the child's head. The child laughs as the stick jumps around. The child is African, and the toy is the African Goliath beetle, the largest insect in the world. 
     The Goliath is a true insect because it has six legs and a body that is divided into three parts. Like all beetles, it has two pairs of wings. The front pair are thick and stiff and protect the back pair, which are soft. It is these soft back wings that make the beetle fly forward. They also cause the loud whirring sound the beetle makes when it flies. To steer, the beetle twists and turns its legs the same way you steer a bike by turning its front wheel. African children often use the Goliath beetle as a toy. Although it is over 15 centimeters long, it is quite harmless. 

E

Think about the different ways that people use the wind.You can use it to fly a kite or to sail a boat.Wind is one of our cleanest and richest power sources（来源），as well as one of the oldest.Evidence shows that windmills（风车）began to be used in ancient Iran back in the seventh century BC.They were first introduced to Europe during the 1100s,when armies returned from the Middle East with knowledge of using wind power.

For many centuries, people used windmills to grind（磨碎）wheat into flour or pump water from deep underground.When electricity was discovered in the late 1800s,people living in remote areas began to use them to produce electricity.This allowed them to have electric lights and radio.However,by the 1940s when electricity was available to people in almost all areas of the United States,windmills were rarely used.

During the 1 970s,people started becoming concerned about the pollution that is created when coal and gas are burned to produce electricity.People also realized that the supply of coal and gas would not last forever.Then,wind was rediscovered,though it means higher costs.Today,there is a global movement to supply more and more of our electricity through the use of wind.