第二节(共5小题;每小题2分，满分10分)

　　根据短文内容，从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

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

　　People have used secret codes for thousands of years. 

　　36 Code breaking never lags (落后) behind code making. The science of decoding and reading coded messages is called cryptography.There are three main types of cryptography.

　　37 For example, the first letters are “My elephant eats too many eels” spell out the hidden message “Meet me.”

　　38 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 “1 3 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.

　　39 For example, “bridge” might stand for “meet” and “out” might stand for “me”. The message “bridge out” would actually mean “Meet me”.

　　40 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 a 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.

　　36.【解析】D

　　本题考察是逻辑关系，根据下一句“code breaking never lags behind code making”可知上一句是只要出现密码，就会有人去解码，故选D。

　　37.【解析】E

　　本题考察是句子之间的例证关系，从后面文章的举例中“For example, the first letters are ‘My elephant eats too many eels’ spell out the hidden message ‘Meet me.’ ”那么前一句应该是对例子的概括，即我们可以知道是运用每个单词的首字母来组成密码，E选项正确

　　38.【解析】G

　　本题考察是文章的篇章结构，前一段是讲到了第一种方法，根据篇章结构，下一段应该是讲述第二种设置密码的方法，而根据该段的例子，即字母表中字母排列顺序转化成为数字信息，所以这里关键词是another way 还有alphabet，故选G。

　　39.【解析】F

　　本题考察的是逻辑关系，从上一句“To read the message of a real code, you must have a code book ”你需要借用解码书来找出密码单词所对应真正意思，F选项表示你应该找出解码书中密码所代表的词语，故F正确。

　　40.【解析】A

　　本题考察的是关键词以及转折关系，根据下一句出现“it is also hard to keep a code book secret for long, ” 这里出现了also hard,所以上一句关键词为hard;另外however表示转折关系，证明上一句与下一句表达的意思相反，即上一句应该没有解密书，是很难去完成解密工作，故A正确。