Modern graffiti began in big cities in the United States in the 1970s. In New York, young people wrote their names, or 'tags', in pen on walls around the city.

    One of the first 'taggers' was a teenager called Demetrius. His tag was TAKI 183. He wrote his tag on walls and in stations in New York. He did it just for fun and he had never imagined his behavior would have launched an amazing art campaign. Other teenagers saw Demetrius's tag and started writing their tags too. Soon, there were tags on walls, buses and trains all over New York.

    Then, some teenagers started writing their tags with aerosol paint. Their tags were bigger and more colourful. Aerosol paint graffiti became very popular in the 1970s and 1980s. It appeared on trains, buses and walls around the world.

    In the 1990s and 2000s, a lot of graffiti artists started painting pictures. Some artists' pictures were about politics. Other artists wanted to make cities beautiful and painted big, colorful pictures on city walls.

    In some countries, writing or painting on walls is a crime. Sometimes, graffiti artists have problems with the police. In other countries, artists can draw and paint in certain places. For example, in Taiwan, there are 'graffiti zones' where artists can paint on walls. In São Paulo in Brazil, street artists can paint pictures on walls and houses. Their pictures are colorful and beautiful. Some tourists visit São Paulo just to see the street art!

    In Bristol in the UK, there is a street art festival in August every year. Artists paint all the buildings in a street. Lots of people come to watch the artists and take photos. You can see exhibitions of street art in some galleries too. There have been exhibitions of street art in galleries in Paris, London and Los Angeles.

    More than 10 years ago, it was difficult to buy a tasty pineapple.The fruits that made it to the UK were green on the outside and, more often than not,hard with an unpleasant taste within.Then in 1966,the Del Monte Gold pineapple produced in Hawaii first hit our shelves.

    The new type of pineapple looked more yellowy-gold than green.It was slightly softer on the outside and had a lot of juice inside.But the most important thing about this new type of pineapple was that it was twice as sweet as the hit-and-miss pineapples we had known. In no time, the Del Monte Gold took the market by storm, rapidly becoming the world's best-selling pineapple variety, and delivering natural levels of sweetness in the mouth,up until then only found in tinned pineapple.

    In nutrition it was all good news too.This nice tasting pineapple contained four times more vitamin C than the old green variety.Nutritionists said that it was not only full of vitamins, but also good against some diseases.People were understandably eager to be able to buy this wonderful fruit.The new type of pineapple was selling fast9 and the Del Monte Gold pineapple rapidly became a fixture in the shopping basket of the healthy eater.

    Seeing the growing market for its winning pineapple, Del Monte tried to keep market to itself.But other fruit companies developed similar pineapples.Del Monte turned to law for help, but failed. Those companies argued successfully that Del Monte's attempts to keep the golden pineapple for itself were just a way to knock them out the market.

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。

    Blind people usually possess one advantage over other people who can see. Their sense of hearing is far more acute. Bats, whose sight is poor, use a sound location system to help them avoid blocks in the dark. They send out pulses of sound waves, pitched at 50,000 cycles per second, far above the limits of the human ear, which can hear sounds up to frequencies of about 20,000 cycles per second. As the echoes bounce back off obstacles such as trees and walls, the bats are able to take proper action.

    The first steps to help blind people to see with sound are based on exactly the same principle. The sound is given off by an ultrasonic (超声的) torch, whose shape is different from a normal electric torch. It is double-barreled. It works in a similar way to a sonar (声呐) unit on a warship or submarine. The unit's transmitter sends out pulses of ultrasonic waves at the same frequency as the bat and the receiver picks up the returning echoes. Because these are still above the frequency at which the human ear can pick them up. The echoes are filtered (过滤) through circuits that turn them into “bleeps” which can be clearly heard before passing them into headphones.

    This means that a person holding the torch can point it ahead of him and scan the area for obstacles over a range of about 25 feet. If there are no return echoes coming through the headphones, then there is nothing in the way. If echoes do come back, then the closer the obstruction the faster the succession of bleeps and the deeper the pitch of each bleep. With practice, the torch could help a blind person to lead a more normal life.

    At present, the experimental ultrasonic torch requires a shoulder bag to carry the batteries, cables for the power supplies and earphones, as well as the torch itself. Fortunately, reducing the size of the electronic equipment is progressing and it should not be long before the whole set-up can be reproduced in a form small enough to fit into a pair of glasses. The wearer would face in the direction he wanted to check, and lift or lower his head just as a sighted person would.

    You may think, salt is just a simple cooking element we shake on our food for a little extra taste. But salt is much more than that. Without salt our muscles would not move. Our nervous systems would not operate. Our hearts would not beat.

    But do not think rubbing salt in a wound will help. Doing that would be painful and not heal the wound. To rub salt in a wound is an idiom that means to purposefully make a bad situation worse.

    Early humans got the salt they needed to stay alive from the animals they killed. But advances in agriculture led to a diet low in salt. So, humans needed to find other sources. Those who lived near the ocean or other natural sources for salt were lucky. Those who did not had to trade for salt. In fact, people used salt as a method of payment in many parts of the ancient world. The word “salary” comes from the word “salt”.

    Salt also played an important part in population movement and world exploration. Explorers understood that if they could keep food fresh, they could travel longer distances. So they used salt to preserve food and explored the world.

    Salt was so important that, according to food historians, it was traded pound-for- pound for gold. Today, people still use the expressions “to be worth one's salt” or “worth one's weight in salt”. The expressions describe a person of value.

    A person might also be called “salt of the earth”. That description means he or she is dependable and trustworthy. However, when you say “I think we should take what he said with a grain of salt” you mean you accept it but maintain a degree of doubt about its truth.

    One of the main decisions you must make when traveling is deciding where to stay. A place to stay can often make or break a holiday. Whether you are looking for a classy hotel or a night under the stars, we can guide you through your different options.

    Bed and Breakfast

    An English invention, bed and breakfasts, offers exactly what they suggest, a bed for the night and breakfast in the morning. “B&Bs”，are usually someone's private home, often found in the countryside.

    Hostels

    For those traveling on a tight budget, hostels are the best accommodation option. Informal places usually with a lovely relaxed atmosphere, they offer dormitory beds for rent. Bathrooms are usually down the hall.

    Remember to check reviews by previous guests online before you book your hostel.

    Couch Surfing

    An unusual but interesting option, couch(沙发) surfing is a growing trend among young internationals. The idea is that you become a member of the online couch-surfing community (www. couchsurfing. com) and then when you travel, look up other members in that country and ask to stay on their couch. Most hosts will suggest sightseeing trips and take you out in the evening, making it a great way to see things that aren't in your guidebook. And remember, it may be free but don't forget to offer to buy your host a drink or dinner.

    Camping

    Sleeping under the stars! For budget travelers staying at camping grounds is the cheapest way to travel. The drawback is having to carry a tent with you. Camping grounds can be found across Europe, America and Australia. However, if you intend on camping in busy cities check first where the nearest place for camping is. More often than not, they are on the edge of cities, which can mean lengthy bus rides into town when you want to eat or see the sights.

    "Cleverness is a gift while kindness is a choice. Gifts are easy – they're given after all. Choices can be hard." –– Jeff Bezos.

    I got the idea to start Amazon 16 years ago. I came across the fact that the Internet usage was growing at 2,300 percent per year. I'd never seen or heard of anything that grew that fast, and the idea of building an online bookstore with millions of titles was very exciting to me. I had just turned 30 years old, and I'd been married for a year. I told my wife MacKenzie that I wanted to quit my job and go to do this crazy thing that probably wouldn't work since most start-ups don't, and I wasn't sure what to expect. MacKenzie told me I should go for it. As a young boy, I'd been a garage inventor. I'd always wanted to be an inventor, and she wanted me to follow my passion.

    I was working at a financial firm in New York City with a bunch of very smart people, and I had a brilliant boss that I much admired. I went to my boss and told him I wanted to start a company selling books on the Internet. He took me on a long walk in Central Park, listened carefully to me, and finally said, "That sounds like a really good idea, but it would be an even better idea for someone who didn't already have a good job." That logic made some sense to me, and he persuaded me to think about it for 48 hours before making a final decision. Seen in that light, it really was a difficult choice, but finally, I decided I had to give it a shot. I didn't think I'd regret trying and failing. And I believed I would always be haunted(萦绕)by a decision to not try at all.

    After much consideration, I took the less safe path to follow my passion, and I'm proud of that choice. For all of us, in the end, we are our choices.