Secret codes(密碼)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 “135520135.”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.

練習(xí)冊(cè)系列答案
相關(guān)習(xí)題

科目:高中英語(yǔ) 來(lái)源:2016-2017學(xué)年河北省高二下學(xué)期第一次月考英語(yǔ)試卷(解析版) 題型:七選五

Americans are obsessed (著迷的) with telling their life stories. This phenomenon isn’t simply the product of the technological world. 1. People are eager to tell stories and are fascinated by those of others. Even at preschool, “sharing time” is a common Monday-morning activity where the teenagers will sit in a circle and take turns telling a story about something they did over the weekend.

2. In many Asian countries, talking about and drawing attention to oneself can be seen as socially inappropriate. People are often unwilling to share their life stories and do not encourage others to do so. But there are also times Asians do share their stories. 3. Asians believe that a person is largely decided by his or her social status and relationships, leaving little reason to broadcast detailed and revealing personal stories to establish a unique self.

Ironically, the more unique Americans strive to be, the greater their need to feel connected with others. In their culture of individuality, relationships are highly mobile and can be easily formed or dissolved(破裂).

Sharing personal stories brings them closer through the exchange of thoughts, feelings and desires. 4. But this motivation is not nearly as strong among Asians, for whom social relations are generally unconditional, obligatory(義不容辭的) and stable, and therefore require little maintenance(維護(hù)).

5. American parents encourage children to share their stories and create opportunities to re-experience the past with children. Asian parents, by contrast, engage their children in telling personal stories less frequently. When they do talk about a child’s experiences, they are not particularly concerned with parent-child bonding but tend to focus on disciplining the child.

A. They tend to focus more on outer facts than personal details.

B. It helps them shape their “selves” and makes them who they are.

C. Interestingly, this obsession is not necessarily shared in other cultures.

D. Talking about personal stories is to cheer people on with positive feelings.

E. It connects them like many different points, holding their society together.

F. Sharing personal stories is also an essential part in everyday conversations.

G. Parents in America and Asia differ in how they share memories with children.

查看答案和解析>>

科目:高中英語(yǔ) 來(lái)源:四川省2016-2017學(xué)年高二5月月考英語(yǔ)試卷 題型:完形填空

“Stop that man!” Vernon shouted. “He has a bomb!” Everywhere, passengers were ____ their feet and screaming. Guerrero stopped with his ____ to the toilets. “___ away from me!” he shouted.

“Guerrero, listen to me!” Vernon ____ him over the heads of the others. There was a silence as Guerrero ____ back at him.

“We know who you are,” Vernon went on. “And we know ____ you' re trying to do. We know all about the insurance and the bomb. That ____ that the insurance is no ___. Do you understand? It's worth nothing. If you die you'll die for nothing and your family will get nothing. ___ than that, they'll be blamed and made to ____ . Think of that, Guerrero.”

Guerrero hesitated. Vernon kept talking and hoped that Guerrero would ___ him.

A man came out of one of the ____ behind Guerrero. At the ____ of the door opening, he ___.

“Get the guy with the case! He's got a bomb. ” Somebody shouted.

Guerrero ____ past the man and ran into the toilet. He had not really understood ____ that had happened in the last few minutes, but he understood that, ___ so many things in his life, his great plan had ___. His life had been a failure, and now his ____ would be a failure too.

As he pulled the string(導(dǎo)火索), he wondered ____whether the bomb would be another failure. In the last second of his life he learned that it was not.

1.A. running over B. jumping over C. running to D. jumping to

2.A. back B. body C. side D. face

3.A. Walk B. Take C. Stay D. Put

4.A. cried out B. called to C. shouted at D. spoke against

5.A. stared B. fought C. talked D. hit

6.A. that B. what C. how D. when

7.A. tells B. explains C. means D. expresses

8.A. harm B. good C. value D. profit

9.A. Sooner B. Better C. Rather D. Worse

10.A. suffer B. worry C. argue D. fight

11.A. hear B. listen to C. see D. look at

12.A. toilets B. kitchens C. seats D. passages

13.A. movement B. sight C. sign D. sound

14.A. hid B. fell C. turned D. rolled

15.A. pushed B. walked C. rushed D. hurried

16.A. everything B. anything C. nothing D. something

17.A. unless B. after C. like D. as

18.A. lost B. broken C. failed D. removed

19.A. power B. life C. plan D. death

20.A. proudly B. bitterly C. excitedly D. curiously

查看答案和解析>>

科目:高中英語(yǔ) 來(lái)源:黑龍江鶴崗一中2016-2017學(xué)年高二下學(xué)期期中考試英語(yǔ)試卷 題型:短文填空

Have you ever had a case 1. a mistake helped you understand an idea or a skill? For me, it was sailing. I took a sailing class when I was in high school. No matter how many times I read the 2. (explain), I could not understand the difference between a “tack" and a “jibe”---two methods of turning a boat ---one much 3. (safe) than the other. Later, one day, when I was sailing, a heavy wind blew up. We needed to head back, 4. I mistook the “tack” for the “jibe” and pushed the boat in the wrong direction. Before I realized 5. (I) mistake, it was too late. Luckily, no one 6. (hurt). Only after this experience did I 7. (clear) understand the sailing phrase “turning on the wind” that I 8.(read) so many times in the textbook.I never confused a “jibe” with a “tack” again! Now I often share this story 9. my students after they have made mistakes. I hope they can learn something from their mistakes and correct them instead of10. (regret) all day.

查看答案和解析>>

科目:高中英語(yǔ) 來(lái)源:黑龍江鶴崗一中2016-2017學(xué)年高二下學(xué)期期中考試英語(yǔ)試卷 題型:閱讀理解

Calvin Gillian didn’t believe that Norway was the place for an adventurous holiday. However, some friends told him to go there and he loved it.

“I’m an extreme-sports maniac. I’ve traveled to many different countries, but I didn’t expect Norway to be a good place for an extreme holiday. Tourists usually visit Norway because of its old Viking history or to go fishing and boating in the famous fjords(峽灣) to enjoy a relaxing holiday, or to go climbing to enjoy the beauty of nature. But I didn’t go for fishing; I wanted adventure.

“Skiing is the best thing you can do in Norway. Svartisen, the Black Ice glacier(冰川), is wonderful. The ice is not the usual white but a deep blue color, like the sea. However, you have to wear special clothes, because skiing on a million-year-old glacier can be very dangerous.”

“Then, there is Hunderfossen Family Park for Toll Park. You can go water skiing and ice skating. It is certainly a beautiful place but it is more expensive than visiting other parts of Norway.

“I also visited the Homenkollen Ski Jump in Oslo. The view from the top of the ski jump was wonderful and the the ski museum was very interesting. I wanted to try a jump but unfortunately, it’s only for professional ski-jumpers. Anyway, I was very tired and I needed a break, so I went back to my hotel and got some sleep.

“Next year, I am going to take my girlfriend to Norway, too. She is having her holiday in Australia now and she wants to have a different type of adventure for next year.”

1.How did Calvin Gillian feel about his trip?

A. Bored B. Relaxed

C. Satisfied D. Disappointed

2.The underlined word “maniac”(in para.2) refers to someone who___.

A. has a strong interest in something

B. has a bad opinion of something

C. expects things to be successful

D. likes to compete with others

3.What did Calvin Gillian do in Norway?

A. Ski-jumping B. Climbing

C. Fishing D. Skiing

4.What’s the best title for the text?

A. Calvin Gillian’s Holiday Countries B. Travel in Different Countries

C. Historical Places in Norway D. A Norwegian Adventure

查看答案和解析>>

科目:高中英語(yǔ) 來(lái)源:貴州省2016-2017學(xué)年高二下學(xué)期期中考試英語(yǔ)試卷 題型:書(shū)面表達(dá)

假定你是李華,你校攝影俱樂(lè)部(photography club)將舉辦國(guó)際中學(xué)攝影展。請(qǐng)給你的英國(guó)朋友Peter寫(xiě)封信。請(qǐng)他提供作品。信的內(nèi)容包括:

1.主題:環(huán)境保護(hù);

2.展覽時(shí)間;

3.投稿郵箱:intlphotoshow@gmschool.com.

注意:

1.詞數(shù)100左右;

2.可以適當(dāng)增加細(xì)節(jié),以使行文連貫。

3.提示:國(guó)際中學(xué)攝影展:an International High School Students Photography Show

________________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

___________________________________________________________________

查看答案和解析>>

科目:高中英語(yǔ) 來(lái)源:貴州省2016-2017學(xué)年高二下學(xué)期期中考試英語(yǔ)試卷 題型:閱讀理解

Urban swans might be born with a daredevil gene that makes them less fearful of humans, compared with their rural colleagues.

A study has found swans living in cities tend to be bolder and it is at least partly determined by a gene called DRD4. Birds with this gene could therefore be better adapted to settling in more populated areas, while more timid(膽怯的)swans would escape to less inhabited regions.

It could help to explain why swans in public parks and on urban rivers have a reputation for being so aggressive towards humans - they are simply not afraid of us.

Biologists from some universities in Australia, tracked and collected blood samples from black swans living in two wetlands near cities. One group of swans lived in a recreational urban park, while the other occupied a waste-water processing site out of town. The two areas were less than 20 miles apart. Later, from 2011 through 2013, the researchers started systematically scaring the swans at both sites. The researchers approached the birds and calculated how close they could get before they flew away. As expected, they noticed that while rural swans started flying away if a human was closer than 119 meters, the scientists could come as close to urban swans as 39 meters before taking off.

Analyses of the blood samples, in fact, showed that 83 per cent of the less cautious swans presented the same genetic DRD4 variation(變異)while rural swans have different genetic makeups resulting in more wariness(謹(jǐn)慎,小心).

The researchers conclude that swans with the bold variation of the gene might choose to live in urban environments, as they tend to be less bothered by human presence.

1.The underlined word in paragraph 1 means__________.

A. timid B. cautious

C. bold D. stubborn

2.What’s the difference between rural swans and urban ones?

A. The rural swans carry more DRD4.

B. The urban swans are more friendly.

C. The urban swans are less scared of people.

D. The rural swans are aggressive towards humans.

3.What does DRD4 refer to ?

A. a kind of blood. B. a kind of food.

C. a kind of genetic variation. D. a kind of swan.

4.What does the 4th paragraph mainly talk about?

A. The living habit of swans.

B. The living environment of swans.

C. The contribution of the biologists.

D. The process and result of the research.

查看答案和解析>>

科目:高中英語(yǔ) 來(lái)源:江蘇省徐州市2016-2017學(xué)年高一下學(xué)期期中考試英語(yǔ)試卷 題型:閱讀理解

Many of us remember being in awe(敬畏) when we saw cloned dinosaurs running wild in the film Jurassic Park. And the idea of using technology to revive(恢復(fù)) extinct species has long fascinated not only writers and directors, but scientists as well.

According to The Telegraph, woolly mammoths(長(zhǎng)毛猛犸象), which featured in the popular Ice Age animated movie series, “may walk the earth once more” now that scientists have taken another step toward realizing a long-held dream—recreating their DNA.

Mammoths became extinct around 10,000 years ago. However, since the discovery of near-perfect preserved remains in Arctic permafrost(北極凍土帶) in May 2013, a variety of research studies have been carried out since.

Geneticists from Harvard University analyzed DNA from the remains, looking for genes which separated mammoths from elephants, such as hairiness and ear size. They then used the results to reproduce exact copies of 14 mammoth genes. “It is the first time that mammoth genes have been alive—although so far it has only been done in the lab,” George Church, lead researcher of the project, told the Sunday Times.

Church then used a new technique which allows scientists to edit DNA carefully, replacing sections of elephant DNA with the mammoth genes. So “we now have functioning elephant cells with mammoth DNA in them,” he said.

However, Church ruled out the possibility of bringing the mammoths back to life via cloning from frozen remains. He said he “preferred to focus on rebuilding the full mammoth genome(基因組) by analyzing DNA from preserved remains and putting it into the cells of its closest living relative – the Asian elephant,” reported The Telegraph.

Church argued that the return of the woolly mammoth—or rather, the return of something very similar—could help bring back fragile(脆弱的) ecosystems. However, some scientists believe that bringing back the mammoth would be unethical.

Professor Alex Greenwood, an expert on ancient DNA, said: “We may face the extinction of African and Asian elephants. Why bring back another elephant from extinction when we cannot even keep the ones that are not extinct around?” he told the Sunday Times. “What is the message? We can be as irresponsible with the environment as we want. Then we’ll just clone things back?”

“Money would be better spent focusing on conserving what we do have than spending it on an animal that has been extinct for thousands of years,” he said.

1.We can learn from the article that ______.

A. cloned mammoths followed cloned dinosaurs to get revived

B. the technology to revive mammoth genes is already mature

C. George Church and his colleagues tried to reproduce mammoth DNA

D. Church and his team managed to list all the genes that separate mammoths from elephants

2.According to Church, what is the significance of his study?

A. It could help prevent the extinction of the Asian elephant.

B. It could help people better tell elephant DNA from mammoth genes.

C. It could help bring back some extinct species and save fragile ecosystems.

D. It could help bring mammoths back to life via cloning from frozen remains.

3.The underlined word “unethical” in Paragraph 7 is closest in meaning to ______.

A. unacceptable B. misled

C. impractical D. illegal

4.According to the article, Professor Alex Greenwood believes that _______.

A. there is no need to worry about the extinction of African and Asian elephants at present

B. it’s necessary to bring back species that are beneficial to human beings from extinction

C. the return of the woolly mammoth would help to balance ecosystems

D. it’s more important to protect present species than to bring back extinct ones

查看答案和解析>>

科目:高中英語(yǔ) 來(lái)源:四川省畢業(yè)班第三次診斷性考試英語(yǔ)試卷 題型:閱讀理解

Sometimes life trips you up,but knowing how to approach failure can be the first step to success. When author J. K. Bowling addressed the graduating class at Harvard last June,she didn't focus on success. Instead,she spoke about failure. She related a story about a young woman who gave up her dream of writing novels to study something more practical. However,she ended up as an unemployed single mom. But during this hard time,she realized she still had a wonderful daughter,an old typewriter,and an idea that would become the foundation for rebuilding her life.“Perhaps you've heard of Harry Pottery You might never fail on the scale I did,” Bowling told the audience.“But it is impossible to live without failing at something,unless you live so cautiously that you might as well not have lived at all. You will never truly know yourself , or the strength of your relationships,until both have been tested by hardships. Such knowledge is a true gift, for it is painfully won,and it has been worth more to me than any qualification I ever earned.”

Lots of Americans are tasting failure for the first time now and immediately trying to spit it out. Whether it's unemployment, or the evaporation(消失)of hard-earned savings, the have-it- all generation suddenly lose everything they own. But in the bitterness that accompanies hardships are lessons worth savoring-and,if you look hard enough,sweet opportunity.

Next,you'll learn how the brain responds to failure and how it can be reprogrammed for success using some simple tricks. You'll also find advice from a successful entrepreneur(企業(yè)家)who claims that times like these are actually among the best for launching dreams. But most valuable,you'll meet some ordinary people who were in some tough situations. A few cheered up; others got depressed. But even though their stories are quite different,the outcomes are the same. They all bounced back. And you can too.

As Bowling herself would admit, it doesn't take a wizard(奇才)to do it.

1.We learn from Paragraph 2 that .

A. college students have never suffered a defeat

B. it is normal for you to fail at something in life

C. if you are very cautious,you can enjoy your life

D. you need a daughter and a typewriter to succeed

2.Which of the following statements would J. K. Bowling agree toy

A. The knowledge we accumulate is a true gift for us.

B. Our experience is more valuable than qualifications.

C. We can understand ourselves better in time of danger.

D. Our bitter experience helps us to realize our strength.

3.The underlined word “savoring" in Paragraph 3 probably means .

A. learning B. enjoying

C. experiencing D. absorbing

4.What did some ordinary people do in some tough situations according to the text

A. They remained in high spirits. B. They took their fate lying down.

C. They decided to give up and quit. D. They insisted until succeeded.

查看答案和解析>>

同步練習(xí)冊(cè)答案