David’s got a text message from his friend Sam．Can you understand it?

　　7,15　　20,15　　20,8,5　　16,1,18,11

　　This message was in code(密码，代码)．How many letters are there in the English alphabet?Twenty-six．So can you read it now?

　　David decided to use a different code in his answer to Sam．This time, he was putting A instead of B, B instead of C, and so on．His message to Sam shown on the right was very short．Can you understand?

　　Sam guessed David’s code, and he replied：ZESDQ RBGNNK．When David’s little sister saw the message, she felt puzzled．She couldn’t read it at all．But David was very happy that his sister couldn’t read his message!

　　Lots of people use codes to send secret messages．In a war, secrets are very important so soldiers often send each other messages in code．Nowadays, we can use computers to make and break difficult codes．Even before computers, people invented other machines to do this．

　　Here’s a famous machine that Germans used in the Second World War(1941－1945)．It’s called the Enigma Machine．The machines were very big, heavy and expensive．Every day they changed the codes automatically, and this made it almost impossible for anyone to break the codes．The person sending a message had one machine, and the person receiving the message had another．

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完形填空阅读下面短文, 掌握其大意, 然后从各题所给的四个选项(A、B、C和D)中, 选出最佳选项. "You can have the same neighbour __1__ years," the old man said. "You love them, or you think you love them, and you hope that they love you. __2__ do you ever really understand them " Charlie Kemp and his family live __3__ door to me for fifteen years. We were good friends for all that time. I enjoy friendship桰'm sure it's the __4__ in the world. They were interesting and clever people, but they were always __5__. For example, their house caught fire twice, and twice the whole family __6__ in mine. They were always __7__ things梞oney, keys, a watch, a car. I often __8__ in the morning and thought: What will __9__ to them today I was their neighbour and friend. Life was always __10__, never dull(枯燥). Best of all, I like the whole family. One day I made a fire in __11__ and was burning some tree leaves. After a time Charlie Kemp came __12__ his house and walked up the road. "Morning, Charlie," I said. "Lovely day, isn't it " He smiled at me. I went on with my work. Twenty minutes __13__ a policeman arrived. He walked into my garden and said. "You'll have to put that fire out. Your neighbour had telephoned us. He __14__ the smell. " "My neighbour. . . "I said. "Yes. "the policeman __15__ his notebook and read, "Charlie Kemp. He lives next door, doesn't he "

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