根据短文内容，从下边的A—F选项中选出能概括每一段主题的最佳选项。选项中有一项为多余选项。
A . The different structure of blue holes.
B. Why scientists are interested in blue holes.
C. How a blue hole comes into being.
D. Blue holes exploring is becoming popular.
E. Rules to obey when diving into blue holes.
F. The general definition of a blue hole.
1.______________
A blue hole is a flooded sea cave with a hole that opens up at the land's surface. These cave systems form in carbonate rock, often on islands. Some blue holes have very special rock formations and water chemistry. Far below sea level, they contain some of the harshest environments on Earth, with no oxygen and no light. Yet these areas are filled with life forms that have adapted to the extreme conditions.
2.___________
Blue holes get their name from the color some have when seen from the air. The color is usually a reflection of the sky on the water. Blue holes are the result of erosion in which water breaks down rock. Rain falling thousands of years ago contained chemicals which slowly wore away at the limestone landmass. These holes later filled with sea water as the sea level changed. The rising and falling of sea levels and the mixture of salt and fresh water further wore away at these cave formations.
3. ____________
These flooded cave systems can be found in the ocean, or they can be found inland. Ocean caves are affected by tides, so they always have water movement. But blue holes on land are very still. They have several layers of water, chemicals, and bacteria. The top layer of fresh water comes from rainfall. This layer acts like a cap on top of the layered mixture, and keeps out oxygen from the atmosphere. The fresh water floats on a denser layer of saltwater. Underneath this is a layer of poisonous hydrogen sulfide, produced by bacteria living in the water. Underneath this layer is anoxic seawater -- water that does not contain any oxygen.
4.___________
Information gathered from these blue holes is helping scientists to increase their understanding of biology, archaeology and geology. But exploring these blue hole environments brings danger as well as discovery. Scientists are interested in these caves because oxygen-free conditions there are similar to those on Earth long ago, before oxygen existed on our planet. But there are many difficulties involved in diving into blue holes.
5.___________
One reason blue holes have not been fully explored is that they can be extremely dangerous. There are many safety rules that divers must follow to help ensure their survival. First, divers must have training and experience to swim in these caves. Divers who explore a cave for the first time must establish a thin rope called a guideline. This line helps them to safely enter and exit the cave without getting lost.
Europe’s deadly outbreak of a rare form of E. coli bacteria (大肠杆菌) has brought new attention to food safety issues. One of the problems when people get sick from food is that the simplest question is often difficult or even impossible to answer. Just what did the people eat that made them sick?
Of course, one way to avoid these medical mysteries is to keep dangerous organisms out of the food supply. This is easier said than done, but scientists keep looking for new ways.
Scientists in the United States have developed an experimental system that uses a high-tech optical scanner. The system is designed to identify the presence of contaminants(致污物) like soil or animal waste on fresh produce. These can be sources of E. coli. E. coli bacteria naturally live in the intestines(肠) of humans and many animals. Most kinds of E. coli are harmless but some can make people sick.
The new scanner can also show damage and imperfections that might make the produce unappealing to shoppers.
Scientists designed the system at a Department of Agriculture research center in Beltsville, Maryland. Moon Kim of the Agricultural Research Service led the team.
MOON KIM: “We were requested, we were asked, to develop a method to detect contamination in produce. So we started with the apple as the model sample.”
The scanner uses a high-speed camera placed over the conveyer belt that moves the produce along. As the apples move along the belt, the scanner captures images of each piece of fruit.
Moon Kim says the team hopes the system will be available before long.
MOON KIM: “We are targeting for development in commercial plants for the next several years.”
The scanner can direct a sorting machine to separate the bad apples from the good ones. The system is currently able to show the surface of only half the apple as it speeds by. The inventers hope to improve the process so it can show the whole surface.
1.What is the main topic of the text?
A. Bacteria. B. A high-tech scanner. C. A camera D. Food safety.
2.E. coli bacteria ______.
A. broke out all over the world B. comes from soil or animal waste
C. is extremely harmful to health D. does not cause illness
3.The high-tech scanner ______.
A. can help to sort out different fruits
B. make the produce appeal to shoppers
C. can only capture images of the whole apple
D. can identify the presence of contaminants
4.What can be inferred from the text?
A. The scanner needs to be improved.
B. The scanner will be available in the next several years.
C. Moon Kim is unwilling to develop the scanner.
D. The scanner is connected to a sorting machine.
Until the 1980s, the American homeless population is mainly made up of older males. Today, homelessness strikes much younger part of society. In fact, a 25-city survey by the U. S. Conference of Mayors in 1987 found that families with children make up the fastest growing part of the homeless population. Many homeless children gather in inner cities; this transient(变化无常的) and frequently frightened student population creates additional problems — both legal and educational — for already overburdened urban school administrators and teachers.
Estimates of the number of homeless Americans range from 350,000 to three million. Likewise, estimates of the number of homeless school children vary radically. A U.S. Department of Education report, based on state estimates, states that there are 220,000 homeless school-age children, about a third of whom do not attend school on a regular basis. But the National Coalition for the Homeless estimates that there are at least two times as many homeless children, and that less than half of them attend school regularly.
One part of the homeless population that is particularly difficult to count consists of the “throwaway” youths who have been cast of their homes. The Elementary School Center in New York City estimates that there are 1.5 million of them, many of whom are not treated as children because they do not stay in family shelters and tend to live by themselves on the streets.
Federal law, the Stewart B. McKinney Homeless Assistance Act of 1987, includes a section that addresses the educational needs of homeless children. The educational provisions（规定） of the McKinney Act are based on the belief that all homeless children have the right to a free, appropriate education.
1.It is implied in the first paragraph that ____.
A. the writer himself is homeless, even in his eighties
B. many older homeless residents are going on strike in 25 cities
C. there is a serious shortage of academic facilities
D. homeless children are denied the opportunity of receiving free education
2.The National Coalition for the homeless believes that the number of homeless children is _____.
A. 350,000 B. 1,500,000 C. 440,000 D. 110,000
3.One part of the homeless population is difficult to estimate. The reason might well be ____.
A. the homeless children are too young to be treated as children
B. the homeless population is growing rapidly
C. the homeless children usually stay outside school
D. some homeless children are deserted by their families
4.The McKinney Act is mentioned in this passage in order to show that ___.
A. the educational problems of homeless children are being recognized
B. the estimates on homeless children are hard to determine
C. the address of grade-school children should be located
D. all homeless people should have free education
GET YOUR DEGREE AT HOME!
Have you ever wondered what a Degree might be worth to you in your job or career(事业)? It means a lot of Americans with an Associate Degree average nearly $10,000 more in yearly earnings than those with just a High School Diploma(毕业证).
Harcourt Learning Direct offers you a way to get a Specialized Associate Degree in 11 of today’s growing fields-without having to go to college full time. With Harcourt, you study at home, in your spare time__so you don’t have to give up your present job while you train for a better one. Choose from exciting majors like Business Management, Accounting, Dressmaking ＆Design, Bookkeeping, Photography, Computer Science, Engineering, and more! Your training includes everything you need! Books, lessons, learning aids__even professional-quality tools and equipment__everything you need to master your training and more ahead to a new career is included in the low tuition(学费) price you pay. Your education is nationally recognized! Nearly 2,000 American companies__including General Electric, IBM, Mobile, General Motors, Ford, and many others__have used our training for their employees. If companies like these recognize the value of our training, you can be sure that employees in your area will, too!
Earn your degree in as little as two years! Get a career diploma in just six months! The career of your dreams is closer than you think! Even if you have no experience before, you can get valuable job skills in today’s hottest fields! Step-by-step lessons make learning easy. Prepare for promotions(提升), pay raises, even start a business of your own! Send today for FREE information about Harcourt at home training!
Simply fill in your name and address on the coupon(票券) above. Then write in the name and number of the one program you’re most interested in, and mail it today. We’ll rush your free information about how you can take advantage of the opportunities(机会) in the field you’ve chosen. Act today!
Mail coupon today!
or call the number below
1-800-372-1589 Call anytime, 24 hours a day, 7 days a week.
www. harcourt-learning.com
E-mail: harcourt@learning.com
1.This advertisement aims at calling on people to ________.
A. attend full-time universities
B. work part time to further their education
C. improve their education at home to get better jobs
D. earn their degrees in different ways that suit them
2.Which of the following is NOT clearly mentioned in this advertisement?
A. The way how you will get your degree.
B. Tuition price.
C. The hot fields you will be preparing yourself for.
D. The length of time it will take you to get a degree.
3.What does the writer of this ad intend to say by naming General Electric, IBM, Ford, etc.?
A. To show that their training is widely used in the country.
B. To show that the training program is fully supported by famous companies in the U. S.
C. To prove the value of their training in every area.
D. To show the importance of getting recognized by the most famous companies.
4.It seems to the writer that the greatest attraction for people to take their training is______.
A. its convenience
B. the degree’s nation-wide recognition
C. the economic benefit it will bring about
D. the hot fields the training will help people to enter
Shopping for clothes is not the same experience for a man as it is for a woman. A man goes shopping because he needs something. His purpose is settled and decided in advance. He knows what he wants, and his objective is to find it and buy it; the price is a secondary consideration. All men simply walk into a shop and ask the assistant for what they want. If the shop has it in stock(有现货的), the salesman promptly produces it, and the business of trying it on follows at once. All being well, the deal can be and often is completed in less than five minutes, with hardly any chat and to everyone's satisfaction.
For a man, slight problems may begin when the shop does not have what he wants, or does not have exactly what he wants. In that case the salesman, as the name implies, tries to sell the customer something else, he offers the nearest to the article required. No good salesman brings out such a substitute impolitely; he does so with skill: “I know this jacket is not the style you want, sir, but would you like to try it for size? It happens to be the color you mentioned.” Few men have patience with this treatment, and the usual response is: “This is the right color and may be the right size, but I should be wasting my time and yours by trying it on.”
Now how does a woman go about buying clothes? In almost every respect she does so in the opposite way. Her shopping is not often based on need. She has never fully made up her mind what she wants, and she is only “having a look round”. She is always open to persuasion; indeed she sets great store by what the saleswoman tells her, even by what companions tell her. She will try on any number of things. Uppermost in her mind is the thought of finding something that everyone thinks suits her. Contrary to a lot of jokes, most women have an excellent sense of value when they buy clothes. They are always on the lookout for the unexpected bargain. Faced with a roomful of dresses, a woman may easily spend an hour going from one rail to another, to and fro, often retracing her steps, before selecting the dresses she wants to try on. It is a laborious process, but apparently an enjoyable one. Most dress shops provide chairs for the waiting husbands.
1.The underlined sentence “the price is a secondary consideration” in the first paragraph means when a man is shopping ______.
A. he buys good quality things, so long as they are not too dear
B. he buys whatever he likes without considering its value
C. he does not mind how much he has to pay for the right things
D. he often buys things without giving the matter proper thought.
2.What does a man do when he can not get exactly what he wants?
A. He buys a similar thing because of the color he wants.
B. He usually does not buy anything.
C. At least two of his requirements must be met before he buys.
D. So long as the style is right, he buys the thing.
3.What is the most obvious difference between men and women shoppers?
A. Men do not try clothes on in a shop while women do.
B. Women bargain for their clothes, but men do not.
C. The time they take over buying clothes.
D. Men go shopping based on need, but women never.
My job was to make classroom observations and encourage a training program that would enable students to feel good about themselves and take charge of their lives. Donna was one of the volunteer teachers who participated in this .
One day, I entered Donna’s classroom, took a seat in the back of the room and . All the students were working a task. The student next to me was filling her page with “I Can’ts.” “I can’t kick the soccer ball.” “I can’t get Debbie to like me.” Her page was half full and she showed no of stopping. I walked down the row and found was writing sentences, describing things they couldn’t do.
By this time the activity aroused my , so I decided to check with the teacher to see what was going on I noticed she too was busy writing. “I can’t get John’s mother to come for a parents’ meeting.” I felt it best not to .
After another ten minutes, the students were to fold the papers in half and bring them to the front. They placed their “I Can’t” statements into an empty shoebox. Then Donna hers. She put the lid on the box, tucked it under her arm and headed out the door. Students followed the teacher. I followed the students. Halfway down the hallway Donna got a shovel from the tool house, and then marched the students to the farthest corner of the playground. There they began to . The box of “I Can’ts” was placed at the of the hole and then quickly covered with dirt. At this point Donna announced, “Boys and girls, please join hands and your heads.” They quickly formed a circle around the grave.
Donna delivered the eulogy (悼词). “Friends, we gathered here today to the memory of ‘I Can’t.’ He is by his brothers and sisters ‘I Can’ and ‘I Will’. May ‘I Can’t’ rest in . Amen!”
She turned the students and marched them back into the classroom. They celebrated the of “I Can’t”. Donna cut a large tombstone from paper. She wrote the words “I Can’t” at the top and the date at the bottom, then hung it in the classroom. On those rare occasions when a student and said, “I Can’t,” Donna pointed to the paper tombstone. The student then remembered that “I Can’t” was dead and chose other statement.
1.A. job B. project C. observation D. course
2.A. checked B. noticed C. watched D. waited
3.A. on B. with C. as D. for
4.A. scenes B. senses C. marks D. signs
5.A. nobody B. somebody C. everyone D. anyone
6.A. curiosity B. suspect C. sympathy D. worry
7.A. and B. or C. but D. so
8.A. insert B. interrupt C. talk D. request
9.A. taught B. shown C. forced D. instructed
10.A. added B. wrote C. made D. folded
11.A. cry B. pray C. dig D. play
12.A. back B. bottom C. top D. edge
13.A. drop B. raise C. fall D. lift
14.A. keep B. thank C. forgive D. honor
15.A. remembered B. punished C. removed D. replaced
16.A. silence B. heart C. peace D. memory
17.A. down B. up C. off D. around
18.A. birth B. passing C. loss D. starting
19.A. awoke B. reminded C. forgot D. apologized
20.A. simply B. hardly C. seriously D. angrily
