题目
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．（1） ____ 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． （2） ____ For example， the first letters of "My elephant eats too many eels" spell out the hidden message "Meet me．" （3） ____ 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 13 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．（4） ____ For example， "bridge" might stand for "meet" and "out" might stand for "me．" The message "bridge out" would actually mean "Meet me．" （5） ____ However， it is also hard to keep a code book secret for long．So codes must be changed frequently．A．It is very hard to break a code without the code book．B．In any language， some letters are used more than others．C．Only people who know the keyword can read the message．D．As long as there have been codes， people have tried to break them．E．You can hide a message by having the first letters of each word spell it out．F．With a code book， you might write down words that would stand for other words．G．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．（1） ____ 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． （2） ____ For example， the first letters of "My elephant eats too many eels" spell out the hidden message "Meet me．"
（3） ____ 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 13 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．（4） ____ For example， "bridge" might stand for "meet" and "out" might stand for "me．" The message "bridge out" would actually mean "Meet me．" （5） ____ However， it is also hard to keep a code book secret for long．So codes must be changed frequently．
A．It is very hard to break a code without the code book．
B．In any language， some letters are used more than others．
C．Only people who know the keyword can read the message．
D．As long as there have been codes， people have tried to break them．
E．You can hide a message by having the first letters of each word spell it out．
F．With a code book， you might write down words that would stand for other words．
G．Another way to hide a message is to use symbols to stand for specific letters of the alphabet．
People have used secret codes for thousands of years．（1） ____ 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． （2） ____ For example， the first letters of "My elephant eats too many eels" spell out the hidden message "Meet me．"
（3） ____ 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 13 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．（4） ____ For example， "bridge" might stand for "meet" and "out" might stand for "me．" The message "bridge out" would actually mean "Meet me．" （5） ____ However， it is also hard to keep a code book secret for long．So codes must be changed frequently．
A．It is very hard to break a code without the code book．
B．In any language， some letters are used more than others．
C．Only people who know the keyword can read the message．
D．As long as there have been codes， people have tried to break them．
E．You can hide a message by having the first letters of each word spell it out．
F．With a code book， you might write down words that would stand for other words．
G．Another way to hide a message is to use symbols to stand for specific letters of the alphabet．
题目解答
答案
（1）D．推理判断题。根据上句People have used secret codes for thousands of years讲人们使用密码已经几千年了，下句The science of creating and reading coded messages is called cryptography．讲密码破译工作。空白处和密码破译有关，D项：只要有密码，人们就试图破解。内容符合语境，连接上下文。故选D.
（2）E．推理判断题。根据后文句子For example， the first letters of "My elephant eats too many eels" spell out the hidden message "Meet me．"例如，"我的大象吃了太多鳗鱼"的第一个字母就拼出了隐藏的信息"遇见我"。这个例子是来证明人们设置密码时往往会利用一些单词的第一个字母作为密码，E项：你可以通过让每个单词的前几个字母拼出来来隐藏信息，符合此内容，故选E.
（3）G．推理判断题。根据下文的句子 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 13 5．"例如，让我们按照从1到26的顺序给字母表中的字母编号。如果我们用一个数字来代替每个字母，那么消息"Meet me"将改为"13 5 5 20 13 5"解释内容可知介绍了密码设置的又一种方法，G项：另一种隐藏信息的方法是使用符号来代表字母表中的特定字母，符合此意，故选G.
（4）F．逻辑关系题。根据下文的例子For example， "bridge" might stand for "meet" and "out" might stand for "me．" The message "bridge out" would actually mean "Meet me．"例如，"bridge"可能代表"meet"，"out"可能代表"me"，"bridge out"实际上意味着"meet me". 及上句中的a code book可以判断该句是介绍密码本的使用，F项符合此意，承上启下。故选F.
（5）A．归纳总结题。根据上文To read the message of a real code， you must have a code book要阅读真正密码的信息，你必须有一本密码本。介绍密码本的重要作用，A项：没有密码本很难破译，总结上文。故选A.
（2）E．推理判断题。根据后文句子For example， the first letters of "My elephant eats too many eels" spell out the hidden message "Meet me．"例如，"我的大象吃了太多鳗鱼"的第一个字母就拼出了隐藏的信息"遇见我"。这个例子是来证明人们设置密码时往往会利用一些单词的第一个字母作为密码，E项：你可以通过让每个单词的前几个字母拼出来来隐藏信息，符合此内容，故选E.
（3）G．推理判断题。根据下文的句子 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 13 5．"例如，让我们按照从1到26的顺序给字母表中的字母编号。如果我们用一个数字来代替每个字母，那么消息"Meet me"将改为"13 5 5 20 13 5"解释内容可知介绍了密码设置的又一种方法，G项：另一种隐藏信息的方法是使用符号来代表字母表中的特定字母，符合此意，故选G.
（4）F．逻辑关系题。根据下文的例子For example， "bridge" might stand for "meet" and "out" might stand for "me．" The message "bridge out" would actually mean "Meet me．"例如，"bridge"可能代表"meet"，"out"可能代表"me"，"bridge out"实际上意味着"meet me". 及上句中的a code book可以判断该句是介绍密码本的使用，F项符合此意，承上启下。故选F.
（5）A．归纳总结题。根据上文To read the message of a real code， you must have a code book要阅读真正密码的信息，你必须有一本密码本。介绍密码本的重要作用，A项：没有密码本很难破译，总结上文。故选A.
解析
本题为英语阅读填空题，考查学生对语篇逻辑关系的理解和上下文衔接能力。文章围绕密码学的三种类型展开，需根据段落主题和上下文逻辑选择恰当句子。解题核心在于：
- 明确段落主题：每段首句通常提示该段核心内容；
- 分析句子逻辑关系：通过上下文的衔接词、举例等判断空白处应填内容；
- 匹配选项关键词：重点关注选项中与上下文重复或暗示的关键词（如“code book”“symbols”“first letters”等）。
第（1）题
上下文逻辑：前文提到人类使用密码已有数千年，后文引出密码破译的科学（密码学）。空白处需体现密码与破译的同步性。
选项匹配：D选项“只要有密码，人们就试图破解”直接衔接上下文，说明密码与破译的并存关系。
第（2）题
上下文逻辑：本段介绍第一种密码类型——利用单词首字母隐藏信息，后文举例验证。
选项匹配：E选项“通过单词首字母拼出信息”与例子中的“首字母”高度一致，明确主题。
第（3）题
上下文逻辑：本段转向第二种密码类型——用符号代替字母，后文举例用数字替换字母。
选项匹配：G选项“用符号代表特定字母”点明核心方法，与数字替换字母的举例形成逻辑连贯。
第（4）题
上下文逻辑：本段介绍第三种密码类型——用代码符号代替词语，需说明代码本的作用。
选项匹配：F选项“用代码本中的词代替其他词”与后文“bridge out”代表“Meet me”的例子直接对应。
第（5）题
上下文逻辑：总结代码的优点与局限性，强调代码本的重要性。
选项匹配：A选项“没有代码本很难破译”总结上文，同时引出下文“频繁更换代码”的必要性。