growing mountain of electronic waste like computers and personal digital assistants. The electronic waste stream is

increasing three times faster than traditional garbage as a whole.

        Electronic devices contain valuable metals such as gold and silver. A Swiss study reported that while the 

weight of electronic goods represented by precious metals was relatively small in comparison to total waste, the 

concentration (含量) of gold and other precious metals was higher in            So-called e-waste than in naturally 

occurring minerals.

         Electronic wastes also contain many poisonous metals. Even when the machines are recycled and the harmful 

metals removed, the recycling process often is carried out in poor countries, in practically uncontrolled ways which 

allow many poisonous substances to escape into the environment.

         Creating products out of raw materials creates much more waste material, up to 100 times more, than the 

material contained in the finished products. Consider again the cell-phone, and imagine the mines that produced 

those metals, the factories needed to make the box and packaging(包装) it came in. Many wastes produced in the

producing process are harmful as well.

        The U.S. Environmental Protection Agency notes that most waste is dangerous in that “the production, 

distribution, and use of products — as well as management of the resulting waste — all result in greenhouse gas 

release.” Individuals can reduce their contribution by creating less waste at the start — for instance, buying 

reusable products and recycling.

        In many countries the concept of extended producer responsibility is being considered or has been put in place 

as an incentive (动机) for reducing waste. If producers are required to take back packaging they use to sell their 

products, would they reduce the packaging in the first place?

Governments' incentive to require producers to take responsibility for the packaging they produce is usually

based on money. Why, they ask, should cities or towns be responsible for paying to deal with the bubble wrap (气

泡垫) that encased your television?

From the governments' point of view, a primary goal of laws requiring extended producer responsibility is to

transfer both the costs and the physical responsibility of waste management from the government and tax-payers 

back to the producers.

    Many teenagers feel that the most important people in their lives are their friends．They believe that their family members, especially their parents, don't know them as well their friends do．In large families, it is often for brothers and sisters to fight with each other and then they can only go to their friends for advice．It is very important for teenagers to have one good friend or many friends．Even when they are not with their friends, they usually spend a lot of time talking among themselves on the phone．This communication is very important in children's growing up, because friend can discuss something difficult to say to their family members.

    However, parents often try to choose their children's friends for them．Some parents may even stop their children from meeting their good friends．The question of “choice” is an interesting one．Have you ever thought of the following questions?

    Who choose your friends?

    Do you choose your friends or your friends choose you?

    Have you got a good friend your parent don't like?

    It encouraged us to visit Quora. com, the online question and answer community, to find out how users get the most out of every tank of gas.

    Light makes right

    Alex Elderfield noted that excess weight prevents an engine from burning fuel efficiently. "Only carry what is essential in your car, clean out any junk or necessary items otherwise you are paying for the fuel to cart these from place to place," he wrote.

    Driving smoothly — that is, not mashing the gas and then slamming the brakes later down the road — was a fixture of many responses. Quora user Clint Law agreed on that advice, who wrote, "Every little bit of kinetic energy that your brakes lose, your engine burned in fuel to build up." Overbraking should consequently be viewed as wasted acceleration. "That's really what kills your fuel economy," he argued.

    Keep the pressure up

    Keeping the recommended tire pressure for your car was another mantra among Quora users. Marlyn Rosent said she checked her tire pressure every time she filled up her SUV. Quora user Doug Dingus checks his tire pressure every weekend. “Less tire contact means reduced rubbing, requiring less fuel,” he said.

    Air conditioning or windows

    Though the summer heat get many drivers to roll up the windows and turn on the air conditioning, some people argued that running the A/C wastes too much gas. In between were many shades of grey.

    Achilleas Vortselas said it would depend largely on a car's speed. He wrote that as a general rule, people should drive with the windows down around the city and turn the air conditioning on when hitting the highway, where a car's aerodynamic(空气动力的) characteristics would be influenced by opened windows.

    More seriously minded people, however, said to travel as much as possible with windows up and the A/C off. Eddie Xue gets by with just a wisp of outside air. “Use the fan and open your windows every now and then at lower speeds," he wrote.

根据短文内容，选择最佳答案，并将选定答案的字母标号填在题前括号内。

    My parents moved to Mississippi when my brother and I were small children, and we were separated from our Oklahoma grandparents by some 600 miles. This long distance allowed us to only visit our grandparents once a year, either at Christmas or during summer vacation.

    Most of my classmates lived near their grandparents, and I would often hear stories of big families regularly spending time with one another, fishing at “grandpa's” house or going over to “grandma's”for her famous fried chicken. We were disappointed that we did not get to spend more time with our grandparents, but our love for them remained deep and strong.

    We always expected a road trip to Oklahoma. We would count the days, and when the day came, the entire family would pile into our car at four o'clock in the morning. Crossing the Mississippi River into Louisiana, the scenery changed. Crossing the Red River in Oklahoma, we were in a foreign world.

    Every trip to see my grandparents can't be without bringing delight. We jumped out of the car in their driveway to be met with bear hugs. My grandparents wanted to know everything about their grandchildren, and we would sit for hours and tell story after story. Grandma had a meal planned, and you could guess she prepared her grandsons' favorite foods. Of course the best part of the visit was that we were able to do whatever we wanted without punishment from our grandparents. Grandma and Grandpa always had presents for us, short trips planned and lovely surprises, such as the time we got to a local restaurant and ate the world's largest hamburger.

    For thousands of years comets have been a mystery to man. They travel across the sky very fast and have a bright “tail” of burning gas. The comet Tempel 1 has an orbit（轨道） far outside the orbit of the furthest planet in our solar system, Pluto. It has been there for 4.6 billion years, 133 million kilometers from Earth. Last week a little American spacecraft crashed into Tempel 1. The spacecraft had a camera and it took a photograph of the comet every minute before it finally crashed into its surface.

    The space mission to Tempel 1 cost $335 million and was called Deep Impact. The spacecraft was travelling at 37,000 kilometers per hour when it hit the comet and the crash completely destroyed the spacecraft. But before it hit the comet, the spacecraft took some amazing photographs. The last one was a close-up picture which the spacecraft took just 3 seconds before it crashed into the comet.

    “Right now we have lost one spacecraft,” said a delighted NASA engineer. Deep Impact was like a American Independence Day fireworks display. It took many years to plan and ended in an enormous explosion. 

    The spacecraft which crashed into the comet was made of copper and was the size of a washing machine. It was dropped from a mothership into the path of the comet and the mothership then photographed the cloud of ice, dust and organic chemicals that rose from the surface of the comet after the crash.

    The crash completely destroyed the spacecraft but nothing really happened to the comet: experts believe that the crash slowed the comet down by no more than 1/10,000 of a millimeter a second.The aim of the mission was to study for the first time the interior of a comet.

    The mothership was 480 km from the explosion and observed the crash and the explosion with instruments for 800 seconds. Seven satellites, including the Hubble space telescope, watched the moment of drama, and over the next day and night about 50 telescopes on Earth were watching the distant comet.

    The baby is just one day old and has not yet left hospital. She is quiet but alert (警觉的). Twenty centimeters from her face researchers have placed a white card with two black spots on it. She stares at it carefully. A researcher removes the card and replaces it by another, this time with the spots differently spaced. As the cards change from one to the other, her gaze(凝视) starts to lose its focus—until a third, with three black spots, is presented. Her gaze returns: she looks at it for twice as long as she did at the previous card. Can she tell that the number two is different from three, just 24 hours after coming into the world?

    Or do newborns simply prefer more to fewer? The same experiment, but with three spots shown before two, shows the same return of interest when the number of spots changes. Perhaps it is just the newness? When slightly older babies were shown cards with pictures of objects (a comb, a key, an orange and so on), changing the number of objects had an effect separate from changing the objects themselves. Could it be the pattern that two things make, as opposed to three? No again. Babies paid more attention to squares moving randomly(随意地)on a screen when their number changed from two to three, or three to two. The effect even crosses between senses. Babies who were repeatedly shown two spots became more excited when they then heard three drumbeats than when they heard just two; likewise(同样地) when the researchers started with drumbeats and moved to spots.