If you want a more interesting experience when you arrive in a new city or country, here are some better ways to travel, both for you and for the environment.

    Way 1 Get out of the car and walk. It's slower but it's the greenest way to travel. It's also the most rewarding（有益的）way to see a city, but remember to wear comfortable shoes.

    Way 2 Cycling is also  a good choice. Many hotels now  offer free bikes to guests. It is convenient for people to travel around the city. Some also provide electric bikes that make it easier to go up hills and on longer journeys. Some cities also have mobikes, and you can pick up one easily. It's not free but very cheap.

    Way 3 If you have to take transport in a city, try to take public transport. Most cities now offer lots of information and very clear maps at the city's website.

    Way 4 If possible, take buses, trains or ships to travel from city to city. They are usually greener than cars and planes.

    Way 5 When the only way to travel is by car, rent(租) an electric car. Many car rental companies now offer them, so always ask!

    In many high schools, there are strict rules about using mobile phones. If your phone rings in class, for example, the teacher will be very angry.

    Every mobile phone has a ringtone (铃声). It tells you that someone is calling you. Now, there is a ringtone called "mosquitotone (蚊子铃声)". Using it, students can receive calls and text messages (短信) in class but the teacher will not realize what is happening. How?

    Mosquitotone has a special sound. Only children and teenagers can hear it. As we get older, we are unable to hear some sounds with high frequencies (频率). As a result, a child or teenager can hear the mosquitotone ringtone, but someone of 20 or older can't.

    But sometimes, people over 20 can hear the ringtone. One British student's phone uses mosquitotone. In class, the student's phone rang. The 22-year-old teacher looked at the student and became unhappy. "I heard that. You know the rule: no mobile phone in class."

    Not all the students are interested in mosquitotone. Jerry Jones, a high school student of 17, says, "Using mosquitotone too often is bad for our hearing. I may use it for pleasure, but not in class. It's unfair(不公平的) to the teachers!"

    What do parents think of mosquitotone? "I think it is perfect for places like movie theaters," says Connie Neeson, 44. "Think about it. You're watching a film and someone's mobile phone rings. Mosquitotone is good because many people don't hear it. However, it also has a bad influence（影响） on their study if students use it in class."

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    Different weather makes people feel different.It has an effect on health，intelligence(智力) and feelings.

    In August，it is very hot and wet in the southern part of the United States.People there have heart trouble and other kinds of health problems during this month.In the Northeast and the Middle West，it is very hot at some times and very cold at other times.People in these states have more heart trouble after the weather changes in February or March.

    The weather can also influence intelligence.For example，in a 1983 report by scientists, the IQ(智商) of a group of students was very high when a very strong wind came，but after the strong wind，their IQ was 10% lower.The wind can help people have higher intelligence.Very hot weather，on the other hand，can make it lower.Students in many schools of the United States often get worse in exams in the hot months of the year(July and August)．

    Weather also has a strong influence (影响)on people's feelings.Winter may be a bad time for thin people.They usually feel cold during these months.They might feel unhappy during cold weather.But fat people may have a hard time in hot summer.At about 18℃，people feel more comfortable.

    Are you feeling sad，tired，or unhappy today？It may be the weather's problem.

    Artificial intelligence(AI)(人工智能)is the ability of a computer program or a machine. The computer or the machine with AI can think and learn. It is also a field of study that tries to make computers "smart". John McCarthy, a scientist, came up with(提出)the name "artificial intelligence" over 60 years ago. Many things such as learning and problem solving can be done by computers, though not in the same way as people do.

    An unusual goal of AI research is to create computer programs. They can learn, solve problems, and think logically(逻辑地). At present, Al can successfully understanding human speech, recognizie (识别)human faces, operate self-driving cars and compete in some game systems like playing Chess. However, Some people also consider(认为）AI a danger to humans if it develops too quickly. A famous British scientist also was not for this kind of technology.

    Math is the basic language of AI. If students are good at math, they will be more likely to become successful AI designers(设计者)in the future. We need not only bright students, but also average(普通的)students. As for(对于)average students ，if they get enough math skills, they can also become successful AI designers. Besides, a good knowledge of computer science is also necessary for AI designing.

    Scientists hope to create creative(有创造力)and emotional (有感情的)AI. The AI can possibly understand human feelings or create art. Many ways and tools have been tried to discover this wide and exciting field.

    Our life will be different from nowadays with robots appearing in our homes. So what will the future be like? Here are some students' ideas.