Ifyouandyourfriendswishtoshareasecret,youcanwriteitinco...

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問題詳情：

If you and your friends wish to share a secret, you can write it in code, and no one else will be able to read it. Codes are one way of writing in secret. Ciphers （暗碼） are another. In a code, each word is written as a secret code or code number. In a cipher each letter is changed.

Codes and ciphers have played an important role in the history of the world. Julius Caesar, the Roman ruler who defeated almost all the countries in Europe about 2,000 years ago, used a cipher when he sent secret messages to his troops. During the American Revolution, George Washington’s spies used a kind of code to send him information about the enemy before his military（*事的） action. In World War II, the Americans “broke”, or figured out, Japan’s most important navy codes and got enough information to destroy a powerful Japanese fleet.

Storekeepers use codes to mark their goods. The codes show how much was paid for the goods or when they were added to the stock（商品）. Businessmen use codes to hide plans from their business enemies. Sometimes personal letters or diaries are written in code. Many people enjoy figuring out codes and ciphers simply as a hobby.

In the 16th century, codes and ciphers were very popular among scientists. They wrote messages to each other in code so that no one else would learn their secrets. Geronimo Gardano, an Italian astrologer（*家）, mathematician, and doctor, invented the trellis cipher. He took to sheets of paper and cut exactly the same holes in each one. Then he sent one sheet, which he called a trellis, to a friend and kept the other for himself. Whenever he wanted to write a message, he put his trellis over a clean sheet of paper and wrote the secret message through the holes. Then he removed the trellis and filled the rest of the paper with words that would make sense. When his friend received it he put his trellis over the writing and read the secret message.

1．The best title of this passage is .

A．Codes and Ciphers B．Differences between Codes and Ciphers

C．History of Codes and Ciphers D．Inventors of Codes and Ciphers

2．Which of the following statements is true?

A．Ciphers can be broken or figured out more easily than codes.

B．You could read some words in Geronimo’s letter without his trellis.

C．The first person who ever used a cipher in history was Julius Caesar.

D．Fondness of using codes was the hobby of the scientists in the 16th century.

3．According to Geronimo Cardano, a trellis is .

A．a piece of paper with many small holes

B．a secret message with a lot of small holes

C．a letter with unreadable words and sentences