Nuclear power's(核能的) danger to health, safety, and even life itself can be described in one word; radiation(辐射). Nuclear radiation has a certain mystery about it, partly because it cannot be detected (探测) by human senses. It can't be seen or heard, or touched or tasted, even though it may be all around us. There are other things like that. For example, radio waves are all around us but we can't detect them, sense them, without a radio receiver. Similarly, we can't sense radioactivity without a radiation detector. But unlike common radio waves, nuclear radiation is not harmless to human beings and other living things. At very high levels, radiation can kill an animal or human being completely by killing masses of cells (细胞) in important organs (器官). But even the lowest levels can do serious damage. There is no level of radiation that is completely safe. If the radiation does not hit anything important, the damage may not be significant. This is the case when only a few cells are hit, and if they are killed completely. Your body will replace the dead cells with healthy ones. But if the few cells are only damaged, and if they reproduce themselves, you may be in trouble. They reproduce themselves in an unusual way. They can grow into cancer. Sometimes this does not show up for many years.
This is another reason for some of the mystery about nuclear radiation. Serious damage can be done without the knowledge of the person at the time that damage has occurred. A person can be irradiated(放射治疗) and feel fine, then die of cancer five, ten, or twenty years later as a result. Or a child can be born weak or easy to get serious illness as a result of radiation absorbed by its grandparents. Radiation can hurt us. We must know the truth.According to the passage, the danger of nuclear power lies in __________.
| A．nuclear mystery | B．radiation detection |
| C．radiation level | D．nuclear radiation |
Radiation can lead to serious results even at the lowest level ________.
| A．when it kills few cells |
| B．though the damaged cells can repair themselves |
| C．if it damages few cells |
| D．unless the damaged cells can reproduce themselves |
Radiation can hurt us in the way that it can _____.
| A．kill large numbers of cells in main organs so as to cause death immediately |
| B．damage cells which may grow into cancer years later |
| C．affect the healthy growth of our younger generation |
| D．lead to all of the above results |
Which of the following can be best inferred from the passage?
| A．The importance of protection from radiation cannot be too overemphasized (过分强调). |
| B．The mystery about radiation remains unsolved. |
| C．Cancer is mainly caused by radiation. |
| D．Radiation can hurt those who do not know about its danger. |
Suppose you don't need your car today.And suppose，as it happens that a stranger in your area does need a car.Would you be willing to rent yours out?
Several carsharing startups，including Getaround，RelayRides and JustSharelt，are eager to connect car owners with renters this way.The companies have different rules，but participating owners receive，generally speaking，about twothirds of the rental earnings.RelayRides says an owner of a midsize，latemodel sedan who rents out a car for 10 hours a week could expect to clear about $ 3,000 a year.
Peertopeer carsharing remains in the trial stage；it can be found in San Francisco and a few other places.It has a long way to go before it becomes the auto equivalent of Airbnb，the surprise success story for peertopeer sharing of space in apartments and houses.
Shelby Clark，founder of RelayRides，says potential investors in his company have been concerned that owners will be afraid to hand their car over to strangers.To address that，he points to Airbnb，saying，“Letting people sleep in your living room is much more of a disturbance into your personal space than letting someone use your car.”
All of these companies offer their own insurance coverage for their renters，which are supposed to put owners' minds at ease.But only two states—California and Oregon—have passed laws to clarify that an owner will not suffer any consequences should a carsharing renter have an accident.
“In all the other states，legal ambiguity remains，” Shelby Clark says.“If a renter should be involved in a serious accident in those states，the victim can be expected to go after every party possible，including the car's owner.”
Also to remove the worries of car owners，the driving records of renters are checked for recent serious violations..What does the underlined word “sedan” in Paragraph 2 probably refer to?
| A．A kind of car. |
| B．An owner of a car. |
| C．A renting company. |
| D．A carsharing renter. |
Which of the following is true of Aribnb?
| A．It cares little about personal privacy. |
| B．It deals with housesharing successfully. |
| C．It is a very popular carsharing company. |
| D．Its ideas are being tried out in some states. |
If a carsharing renter should have an accident in California，the car's owner ________.
| A．has to take legal responsibility |
| B．will not suffer the consequence |
| C．is not covered by health insurance |
| D．must pay the insurance for the renter |
According to the text，more carowners will participate in the service，if ________.
| A．legal ambiguity is clarified in all the states |
| B．renters are warned not to violate traffic rules |
| C．more money is given to participating owners |
| D．people are aware of the importance of sharing |
It can be learned from the text that carsharing ________.
| A．makes no profit |
| B．remains in popularity |
| C．is against the state law |
| D．is a new business model |
Technology is making life easier for some dairy farmers.They use robotic systems to milk their cows.Cows are trained to follow a series of paths that lead to milking stations.Only one cow at a time can enter a station.
Once inside，the cow is rewarded with food.As the cow eats，a robotic arm cleans and connects the animal to the milking machine.A few minutes later，milking is complete.The gate is opened，the cow is released and the next cow enters.
The robotic systems are designed to operate 24 hours a day.The cows get to decide when they want to be milked.Cows are milked an average of about three times a day.Some are milked four to six times a day.
The cows wear collars around their necks that identify them to the system.A computer keeps records on their eating and milking.A cow is released from the station if the computer decides it should not be milked.
The automated system also measures the temperature and color of freshly produced milk.Milk is thrown away if it does not pass the tests.
Professor Plaut believes the systems will appeal especially to the next generation of farmers.She means young people who are more interested in technology and less interested in working all the time on the farm.Still，she says the price of robotic milking systems will continue to limit their use.
Doug and Tina Suhr have more than 100 cows on their family farm.Last year it became the fourth farm in southeast Minnesota to get a robotic milking system.A recent story in a local agricultural newspaper said the first robot costs 175,000 dollars.The second costs 150,000 dollars.
Doug told AgriNews that wages that would have been paid for one employee in five years will pay for one robot.He says the increase in milk production reaches a high of more than six kilograms per cow per day.From the first paragraph，we can infer ________.
| A．the robotic system is designed to reduce labor |
| B．cows can be raised by robots in the future |
| C．robots direct cows into milking stations |
| D．cows are kept clean by robots on some farms |
Besides milking cows，the robotic system also can ________.
| A．adjust the temperature of milking stations |
| B．judge the quality of fresh milk |
| C．improve the appetite of cows |
| D．keep fresh milk for two weeks |
Why is the robotic system not popular now?
| A．Because young people have no interest in it. |
| B．Because it is difficult to learn how to use it. |
| C．Because people can't afford to buy it. |
| D．Because it usually causes the waste of milk. |
According to Doug，what is the wage of an employee per year?
| A．$150,000～$175,000. |
| B．over $75,000. |
| C．$150,000～$30,000. |
| D．$30,000～$35,000. |
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.What is the main topic of the text?
| A．Bacteria. | B．A high-tech scanner. | C．A camera | D．Food safety. |
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 |
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 |
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.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 |
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 |
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 |
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 |
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E-mail:harcourt@learning.comThis 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 |
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. |
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. |
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 |