Since the beginning of history, man has been fascinated by the idea of living forever, of winning the fight against death and disease. So far, this has only remained a dream, though a very powerful one. Many people have wondered whether it would be possible to find a way to preserve human bodies, and what would be the best way to preserve human bodies.

    It has long been known that meat or fruit can be kept fresh for long periods by freezing; in ancient China, for example, food was stored with ice to keep it fresh. This method could also be useful for preserving humans, and in fact many people have explored this possibility.

    However, most living beings that exist under warm conditions die when frozen. This is because of the harmful effects of freezing ice crystals, which are not only larger than the volume of the water originally in the cells, but also form sharp cutting shapes that harm the cells.

    In the 1940s Dr B. J. Luyet and a group of scientists in England were working on the problem of freezing cells without damaging them. Since the harm caused by ice crystals was the main cause of the damage, Luyet suggested removing some or all of the water from the cells before freezing them.

    Using living cells from chicken, Luyet and his assistants discovered that they could partly dry the chicken cells, using a mixture of the white part of an egg and glycerin, a clear thick liquid made chiefly from fats and oils. Some success was obtained. The chicken cells were dried, frozen for a period of time, and then carefully unfrozen.

    Almost all the cells recovered when they reached normal temperature. Since then, the cooling of whole animals to a temperature very much below freezing point for later unfreezing has become more of a possibility, and the glycerin method would probably be used to accomplish this. When this can be done completely and successfully, science will have moved much closer to its aim of freezing and storing incurable patients until the day they can be cured.

In the USA, about 480,000 school buses take more than 25 million children to and from school. The yellow school bus is a US icon (图符).Yellow became the color of school buses in the USA in 1939.Dr.Frank got the good idea. He said it was easy for people to see yellow buses and the black letters on them in early morning or late afternoon. That would make children safer. The only adult on the bus is the driver.

There are not many school buses in Britain, and they are not yellow. They have trackers(追踪器) on them, so kids are being tracked while they travel to and from school by bus. The trackers let parents know where the school bus is and whether their kids are on the bus.

Kindergarten (幼儿园) is a difficult time for some kids. It's the first time for them to go away from their parents. To make kids love their school, Japanese kindergartens and schools have colorful buses. The buses can easily make children want to take them - and then, go to school. Even some parents want to take them, too!

School buses are becoming more and more popular in China now. It's said that there will be 3,000 yellow school buses on the road by the end of this year in Chongqing. These school buses look just like the American school buses. In China, besides the bus driver, there should be an adult on the school bus to watch the students. If there are more than 40 students, two adults are needed.

The school bus is important in students' everyday lives. It can help the environment and can also keep children safe.

The four great inventions of ancient China are China's outstanding contributions to the whole world, and have had a great impact on world's scientific and cultural exchanges.

The teenager life(青少年生活) is nice. You can enjoy it. You can do many things in your teenager years.

Study hard at school

School life sometimes is difficult, but it is really important in your teenager years. So always do your homework after school first.

Make good friends

You don't need to know everyone at school, but it's important for you to make some good friends. Your friends can make you happy and help you. You don't need many friends. But the quality(质量) of your friends is really important.

Have your hobbies

Seek some interesting things. You can read books, sing songs and play football. Don't be afraid to do new things.

Do volunteer(志愿者) work

This kind of work can make you be good. And it can help you with your study and get good work. It is very good.

 Four students are in the classroom. They are Anna, Tom, Mike and Mary. Their jackets are on the teacher's desk. The jackets are brown, white, red, and blue. But we don't know whose they are. We know the boys' jackets aren't red and the girls' jackets aren't brown. What color is Mary's jacket? We don't know. But we know it's not blue. Tom says, "My jacket is white. " Do you know what color their jackets are?

 More biking, better public transport and odd-even bans on vehicles(车辆单双号限行)— many cities are using different ways to {#blank#}1{#/blank#}(减少) traffic pollution.

 Paris doesn't allow cars in many historic {#blank#}2{#/blank#} (中心的) places at weekends, carries out odd-even bans on vehicles, and makes public transport free w {#blank#}3{#/blank#} there are serious pollution events.

 Because the environment is seriously {#blank#}4{#/blank#} (污染) in Delhi, India made the city stop all new large diesel cars(柴油汽车) and diesel taxis. The city has started odd-even bans on vehicles and is now encouraging Uber-style minibuses. Other cities l {#blank#}5{#/blank#} Dublin and Brussels, are also considering diesel bans.

 Helsinki, capital of Finland, plans to {#blank#}6{#/blank#}(完全地) cut down the number of cars on its streets by developing better public transport, raising the parking prices, encouraging bikes and {#blank#}7{#/blank#}(走路). The government hopes that in this way, no one will want a car by 2050.

 Freiburg, Germany has 500 km of bike routes(路线) and a cheap and convenient public transport system. One town, Vauban, does not allow people to park cars near t{#blank#}8{#/blank#} homes and makes car owners pay €18,000 for a special space near the town. In return for living without a car, the government offers people cheaper {#blank#}9{#/blank#} (房子) to live, free public transport, and many bicycle spaces.

 Copenhagen, Denmark prefers bikes to cars and now has more bicycles than people. Large parts of the city have been closed to cars f{#blank#}10{#/blank#} years and the city plans to become carbon neutral(碳平衡) by 2025.