职称英语 (12)
最新试题
They bought the land in order to build a new office block.
05-09
Do we have to wear these name tags？
05-09
Sunspots
It’s not surprising that sunspots ( 太阳黑子）were observed by ancient astronomers (天文学家）.The largest sunspots on the sun can be seen without a telescope. It was not until the inventiion of the telescope ( 望远镜）in the early 17th century， however, that systematic studies of sunspots could be undertaken. The great astronomer Galileo was among the first to make telescopic observations of sunspots.
Sunspots are regions of extremely strong magnetic fields ( 磁场） found on the sun’s surface. A sunspot has a dark central core known as the umbra. The umbra is surrounded by a dark; ring called the penumbra, where the magnetic field spreads outward. Sunspots appear dark because they are giving off less radiation. They are cooler than the rest of the sun’s surface.
Sunsipots are frequently observed in pairs or in paired groups. The members of a spot pair are identified as the leading spot and the following spot. They are identified by their position in the pair in terms of the direction in which the sun rotates ( 旋转）.
The number of sunspots at any one time varies. A large spot group may consist of as many as 10 groups and 300 spots across the sun. The number of spots changes in a fairly regular pattern called the sunspot cycle. The largest number occurs about every 11 years. At sunspot minimum, there are at most just a few small spots.
The average lifetime of an individual spot group is roughly one solar rotation, which is about 25 days. The most persistent large spots, however, can survive for two to three months.
n the last paragraph the word "persistent" means
05-09
The police crept up from behind and took the gangster by surprise.
05-09
The contract between the two companies will expire soon.
05-09
Teaching students of threshold level is hard work but the effort is very worthwhile．
05-09
She was close to success.
05-09
This table is strong and durable.
05-09
The economy continued to exhibit signs of decline in September.
05-09
Five minutes left,the outcome of the match was still in doubt.
05-09
热门试题
The odd thing was that he didn’t recognize me.
Voice Your Opinion: Change Is Needed in Youth Sports
Everywhere you look, you see kids bouncing a basketball or waving a tennis racquet (网球拍)And these kids are getting younger and younger.In some countries,children can compete on basketball, baseball, and volleybal teams starting at age nine. _______(46) And swimming and gymnastics classes begin at age four, to prepare children for competition.
It’s true that a few of these kids will develop intd highly skilled athletes and may even become members of the national Olympic teams. _____ (47 ) This emphasis on competition in sports is having serious negative effects.
Children who get involved in competitive sports at a young age oOen grow tired of sport. Many parents pressure their kids to choose one sport and devota all their time to it.___________ (48) But 66 percent of the young athletes wanted to play more than onesport —for fun.
Another problem is the pressure imposed by over-competitive parents and coaches. Children are not naturally competitive, In fact, a recent study by Paulo David found that most children don’t even understand the idea of competition until they are seven years old. ___________(49)
The third, and biggest, problem for young athletes is the lack of time to do their homework, have fun, be with Mends — in short, time to be kids. When they are forced to spend every afternoon at sports practice, they often start to hate their chosen sport Researchers found that 70 percent of kids who take part in competitive sports before the age of twelve quit before they turn eighteen. _____ (50) Excessive competition takes away all the enjoyment.
(47)
A
Afterwards there was just a feeling of let-down.
The river widens considerably as it begins to turn west.
His heart gave a sudden leap when he saw her.
The original experiment cannot be exactly duplicated.
共用题干
Messages From the Media1.The weather forecast,a story about the candidates in an election,and movie reviews are examples of messages from the media. A communication medium, of which the plural（复数的）form is media,is a means of communicating a message.Examples of media are television,radio,newspapers, books and the telephone.The media that can reach many people at once are called mass media.2.It is not difficult to think of other messages we receive through the mass media. Every day we get hundreds of them. Think about advertisements,for example,we see and hear these messages almost everywhere we go.Advertisements are important messages,even though they are sometimes annoying. They help us compare and evaluate products.3.Most of us get more information from the media than from the classroom. Think for a moment,about how you learn about local news and events.Do you depend on other people or the media?What about international news?What is the most important source of information for you? People who are asked this question usually answer,"Television".4.Think of all the messages you received today.Perhaps you read a newspaper during break-fast,or maybe you read advertisements on billboards（露天广告牌）on your way to school. Did you listen to a weather forecast or the sports news on the radio this morning?Right now you are getting information through a very important medium of mass communication一a book.5.We use the information we get from radio,television,newspapers,and other media to make decisions and form opinions.That is why the mass media are so important. Editorials and articles in newspapers help us decide how to vote,consumer reports on television help us decide how to spend our money,and international news on the radio makes us think and form opinions about questions of war and peace.
Henry cannot resist the lure of drugs.
The weather was crisp and dear and you could see the mountains fifty miles away.
Music is one of the most beautiful forms of artistic expressions ever invented. In movies and plays, music has an added function： it not only moves people but also can shock people.
Our eardrums can withstand sound within 20 to 80 decibels（分贝）.Once sound exceeds this limit, even beautiful music will become ear-splitting noise and harm health. A strong blast（响声）of high sound can twist and break a solid iron sheet. High sound of 150 decibels can kill a healthy rat.
In movies, sometimes the hero can produce a sound that ordinary people can’t hear and only those who have the same ability can feel. In nature, there is actually sound that is beyond our hearing. In physics，the sound that exceeds 20，000Hz is called ultrasonic（超音波的）.Dolphins, whales and bats can make such high-frequency sound. It does no harm to health.
Sound less than 20Hz is called irrfrasonic（次声）waves. When we move, the air will vibrate. The vibration of air can produce infrasonic waves. As the frequency of infrasonic waves is close to that of people’s internal organs, infrasonic wave may cause resonance（共振）in human bodies. As a result，people’s vision may weaken and internal organs may rupture（断裂）.However, whether an infrasonic wave can be used as a weapon depends on its intensity. If its intensity is very low, it wonJt damage internal organs or a persons health. If the intensity of infrasonic wave exceeds 160 decibels, it is extremely harmful. When wind blows at a force of 3 or 4 over the sea, it will produce infrasonic waves of several decibels. Only typhoons can produce infrasonic waves of over 100 decibels. At present, scientists can only produce infrasonic weapons in the lab with the help of advanced scientific tools and powerful electric power.
It can be found from the last paragraph that infrasonic waves
