Earth is our home. It has air that we can breathe(呼吸). It has water for us to drink. It has plants and animals that we can eat. Earth is not too hot or too cold for us. It has everything we need to live.

    We are on earth, but we call see things that are not on earth. Early in the morning, we can see the sun comes up. All day, the sun seems to move across the sky. Later in the day, we can see the sun goes down. But the sun is not really moving around us. We are the ones who are moving. Every morning, we turn towards the sun. Every night, we turn away from it. Every year, we go around it. Earth is our spaceship. All of us in the spaceship are riding around the sun.

    At night, we can often see the moon and stars. From earth stars look like little points of light because they are so far away. But stars are really big. A star is a great mass of burning gas. It gives off light and heat. Our sun is a star.

    There are eight planets moving around our sun. Earth is the third planet around the sun. Some of the planets have moons. A moon goes around a planet just as a planet goes around a star. Earth has only one moon. Some planets have more.

Doing the Right Things in Britain

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    When you stop a stranger in the street to ask for directions, start by saying “Excuse me….”Also, you should say “Please” when you ask for something, and “Thank you” when people give you something.

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    Smile when you talk to people in shops, restaurants and on public transport, and they will probably smile back.

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    Don't sit or stand too close to people you don't know. Britain people don't often touch each other, and usually say “Sorry” when they touch someone by mistake.

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    Don't ask personal questions like “How old are you?”, “How much do you weigh?” or “Are you married?” You can talk about the weather, or recent TV programs, or football matches.

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    Make sure when to meet someone before you go to his home. It's unusual to call on someone when he isn't expecting you.

A. It is very hard to break a code without the code book.

B. Only people who know the keyword can read the message.

C. As long as there have been codes, people have tried to break them.

D. You can hide a message by having the first letters of each word spell it out.

E. With a code book, you might write down words that would stand for other words.

F. Another way to hide a message is to use symbols to stand for specific letters of the alphabet.

    Secret codes (密码)keep messages private. Banks, companies, and government agencies use secret codes in doing business, especially when information is sent by computer.

    People have used secret codes for thousands of years. {#blank#}1{#/blank#}Code breaking never lags(落后) far behind code making. The science of creating and reading coded messages is called cryptography.

    There are three main types of cryptography. {#blank#}2{#/blank#}For example, the first letters of "My elephant eats too many eels" Spell out the hidden message "Meet me."

    {#blank#}3{#/blank#}You might represent each letter with a number, for example, Let's number the letters of the alphabet, in order, from 1 to 26. If we substitute a number for each letter, the message "Meet me" would read "13, 5, 5, 20, 15, 5."

    A code uses symbols to replace words, phrases, or sentences. To read the message of a real code, you must have a code book. {#blank#}4{#/blank#} For example, "bridge" might stand for "meet" and "out" might stand for "me." The message "bridge out" would actually mean "Meet me." {#blank#}5{#/blank#} However, it is also hard to keep a code book secret for long. So codes must be changed frequently.

    Spending time in a bookshop can be enjoyable. If you go to a good bookshop, no assistant(店员)will come near to you and say, "Can I help you? "You needn't buy anything you don't want. If you want to find some books, the assistant will lead you there and then he or she will go away. He or she seems not to be interested in selling any books at all.

    There is a story about a good bookshop. A student wanted to buy a very useful book in the bookshop. But it was too expensive for him to buy. So every afternoon, he went there to read a little at a time. (One day, however, he couldn't find the book from its usual place. He was leaving when he saw an assistant signing(示意)to him. He was surprised that the assistant pointed to the book in the corner. "I put it there so that people couldn't see it or buy it," said the assistant. Then he left the student to go on with his reading.

    The summer holiday is coming. Try to take some time off from school and have fun. Here are some ideas for planning your summer holiday.

    First of all, joining a club is a good idea! You can join a music club, a sports club or an art club, it's good for your future and the teachers in the club can give you some good advice (建议). You can also make some new friends.

    Doing something good for society (社会) is also great. There are many volunteer programs(志愿者项目) for you to choose, such as looking after the____①___or the young, cleaning the streets, planting trees or keeping the traffic(交通) in order. You know that students can also make the world better.

    Did you ever live with another family? You can join in a program___②____"Meeting a New Family" .Two families exchange their children for some time so that they can learn how to get on well with others.

Summer camps are still popular today. An English summer camp can be a good one. You can not only make friends but also learn English.