The crow （乌鸦） is an ordinary （普通的） bird. It is about twenty inches （英寸） long and black all over. Crows are dirty birds because they live on old bad food. Crows eat a lot of waste food. In this way they are more useful to us than any other bird. They clean up the dirty things in our streets. Crows are always hungry. They look for food all day long, and in the evening you can see them in large numbers flying back to their nests (窝) in the trees. They sleep there at night. Crows are much noisier than other birds. Very often a large number of crows will get together on one house and talk. Sometimes they talk together, and sometimes they do it by talking like human beings (人类). It is easy to tell from(区别) crows' sounds whether they are pleased or angry. Perhaps crows talk a lot because they are friendly birds. A pair of crows will live together all their lives, and if one of them dies, the other one becomes very sad and quiet for the rest of its life and sometimes it dies, too.

    On May 17, 2009, according to the plan, Mike Good and I would take a space walk to the Hubble Space Telescope to repair an instrument. The power supply on this instrument had failed, so it could no longer be used. I would be the person doing the repair and Mike my assistant.

    Working in space is more difficult than you can imagine. As there is no gravity, you can't stand and any slight push can result in tragedy -you can be pushed into space, never be back.

    We got to the telescope. Before we could replace the power supply, we would have to remove from the telescope a handrail fixed with four screws. Having taken out the first three, I found the fourth stripped. I realized that the handrail would not come off, which meant we could no longer be able to replace the power supply and repair that instrument, which meant scientists could no longer look at the universe and find life on other planets.

    I tried all kinds of things, and nothing worked. Then Houston, the control centre on the earth, called up and told me to use the tape to tape the bottom of the handrail and pull it off the telescope. They said it was going to take about 27 kilograms of force for me to do that.

    I knew what it meant: The handrail could be completely pulled off and the safety tether might break, and I might therefore be pushed into space.

    Mike was next to me in his space suit but he could not take over my role. I turned and looked into the cabin where my five crewmates were, and nobody in there had a space suit on. However, I knew they were all looking at me. "Come on Mass, we are all behind you." The telescope must be repaired.

    "Bam!" The handrail came right off. The rest of the walk went well. We finally got the new power supply in. They tried it; turned it on from the ground. The instrument came back to life.

    At the edge of darkness, after about eight hours, I turned around and saw the Earth from our altitude at Hubble, 568 kilometers up. I saw the huge round pure blue globe home planet. It's the most beautiful, magnificent thing I've ever seen. It's like looking into heaven. It's paradise.

    In recent years, a number of Chinese technological innovations (科技创新) have been making waves around the world. Among them, four stand out. They are known as "four new great inventions of modern China. They have made our daily lives more convenient.

    High-speed trains

    China created its first high-speed railway line in 2008. Since then, the number of passenger trips has grown by over 30 percent every year. By 2016, more than 5 billion trips had been taken on China's bullet trains(高铁), according to Xinhua News Agency.

    China is currently working on the next-generation bullet trains that will have a top speed of 400 kilometers per hour. By 2020, one-fifth of the country's 150, 000-km railway network will be used by high-speed trains. This network will link more than 80 percent of major cities across China, said Xinhua.

    Mobile payment

    Mobile payment is turning China into a "cashless society" led by the third-party payment companies like Alipay. For example, instead of paying by cash, customers now pay for goods simply by typing a short password into Alipay app on their mobile devices.

    Users can also pay their bills through Alipay, such as their water and electricity bills. Alipay also supports cross-border(跨境的)online and in-store payment, which allows users to buy things on international websites and apps.

    Shared bikes

    Shared bike services started in Western countries. But China has surprised the world with how

quickly it has adopted dockless(无柱的) shared bikes.

    Unlike traditional bike-sharing method, dockless bikes allow users to simply pick up or park a bike on the street through GPS and smartphone app.

    To unlock a bike, you just need to scan a QR code on a shared bike with a smartphone app. After you finish riding, you can park it at available parking areas, lock it and pay for ride through mobile payment services.

    Online shopping

    With around 751 million internet users, China has been the world's largest and fastest-growing line shopping market.

    Online shopping now accounts for 15. 5 percent of total retail sales in China, according to Xinhua. Thanks to lower costs and fewer licensing requirements(执照要求), it's easier for sellers

to open an online shop in China than a brick-and- mortar shop(实体店).

    It also helped to create jobs of rural areas. In 2016, online shopping created more than 20 million jobs in rural areas, with over 8. 1 million running their own online shops, said Xinhua.

    Autumn in Tibet is very beautiful because there are many fresh and bright colours everywhere.

    In north Tibet, one can travel several hundred kilometres by car and cannot see even a person. No one can be found in the north of Shuanghu-only treeless fields and grasslands. Warm autumn days bring life to all of nature. Wild animals become active, and Tibetan antelopes like to play near the lakes. When they run, sometimes they can reach 80 km an hour, leaving the hungry wolves far behind.

    Autumn in south Tibet is very different from that in north Tibet. Mount Qomolangma in southwest Tibet, the highest mountain on Earth, is world-famous for its beauty. It is over 8, 000metres high. There are over 2,300 kinds of plants and about 300 different kinds of wild animals on Mount Qomolangma.

    It's important to learn about protecting our environment. Here is a 5R rule for us:

    Reduce

    If you want to reduce waste, you should use things wisely(明智地). A larger number of trees are cut down to make paper. If everyone uses paper carelessly, soon we will not have any trees left. Other things are also being wasted, and people don't know what to do with the waste in big cities. So it is necessary to use things wisely.

    Reuse

    You should always think of reusing the usable things before throwing them away. For example, you can give your clothes you do not wear any more to the poor. In a family, you may pass on such clothes to younger brothers or sisters.

    Recycle

    Bottles, cans and paper can easily be recycled. By recycling them we save lots of time and money. For example, Coke cans are sent to a factory, where they are smashed flat (压平) and melted(融化) and the metal things are made for new Coke cans.

    Recover(恢复)

    When you buy a box of apples, there may be a few rotten(腐烂的) apples, you have two choices(选择): One is to throw the whole apples away, or you can cut off the rotten parts and keep the good parts. In the way, you are recovering the eatable(能吃的) parts of food.

    Repair

    If one of the legs of your table is broken, you can repair it. If you want to change for better ones, it is better for you to sell the old things or give them to other people who can use them after doing some repair.