1． 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．
gis在物流中的应用 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 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
2． Is Fresh Air Really Good for You？
We all grew up hearing people tell us to "go out and get some fresh air．" （1） According to recent studies，the answer is a big YES，if the air quality in your camping area is good．
（2） If the air you're breathing is clean﹣which it would be if you're away from the smog of cities﹣then the air is filled with life﹣giving，energizing oxygen． If you exercise out of doors，your body will learn to breathe more deeply，allowing even more oxygen to get to your muscles（肌肉）and your brain．
Recently，people have begun studying the connection between the natural world and healing（治愈）．（3） In these places patients can go to be near nature during their recovery． It turns out that just looking at green，growing things can reduce stress，lower blood pressure，and put people into a better mood（情绪）．Greenery is good for us． Hospital patients Who see tree branches out their window are likely to recover at a faster rate than patients who see buildings or sky instead． （4） It giv
es us a great feeling of peace．
胡 温 （5） While the sun's rays can age and harm our skin， they also give is beneficial Vitamin D． To make sure you get enough Vitamin D﹣but still protect your skin﹣ put on sunscreen right as you head outside． It takes sunscreen about fifteen minutes to start working， and that's plenty of time for your skin to absorb a day's worth of Vitamin D．
A． Fresh air cleans our lungs．
B． So what are you waiting for？
C． Being in nature refreshes us．
D． Another side benefit of getting fresh air is sunlight．
E． But is fresh air really as good for you as your mother always said？
F． Just as importantly， we tend to associate air with health care．
G． All across the country， recovery centers have begun building Healing Gardens．
3． Color is fundamental in home design﹣something you'll always have in every room． A grasp of how to manage color in your spaces is one of the first steps to creating rooms you'll love to live in． Do you want a room that's full of life？ Professional？ Or are you just looking for a place to relax after a long day？ （1） ， color is the key to making a room feel the way you want it to feel．
Over the years， there have been a number of different techniques to help designers approach this important point．（2） ，they can get a little complex． But good news is that there're really only three kinds of decisions you need to make about color in your home： the small ones， the medium ones， and the large ones．
（3） ． They're the little spots of color like throw pillows， mirrors and baskets that most of us use to add visual interest to our rooms． Less tiring than painting your walls and less expensive than buying a colorful sofa， small color choices bring with them the significant benefit of being easily changeable．
Medium color choices are generally furniture pieces such as sofas， dinner tables or bookshelves． （4） ． They require a bigger commitment than smaller ones， and they have a more powerful effect on the feeling of a space．
The large color decisions in your rooms concern the walls， ceilings， and floors． Whether you're looking at wallpaper or paint， the time， effort and relative expense put into it are significant． （5） 亿万未婚夫．
A．While all of them are useful
垂直与平行教学设计B．Whatever you're looking for
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