单选题Extending from Quebec to Alabama, the Appalachian Mountain region is extensive and very {{U}}scenic{{/U}}.
单选题DNA Fingerprinting
DNA is the genetic material found within the cell nuclei of all living things. In mammals the strands of DNA are grouped into structures called chromosomes. With the exception of identical siblings (as in identical twins), the complete DNA of each individual is unique.
DNA fingerprinting is sometimes called DNA typing. It is a method of identification that compares bits of DNA. A DNA fingerprint is constructed by first drawing out a DNA sample from body tissue or fluid such as hair, blood, or saliva. The sample is then segmented using enzymes, and the segments are arranged by size. The segments are marked with probes and exposed on X-ray film, where they form a pattern of black bars—the DNA fingerprint. If the DNA fingerprints produced from two different samples match, the two samples probably came from the same person.
DNA fingerprinting was first developed as all identification technique in 1985. Originally used to detect the presence of genetic diseases, it soon came to be used in criminal investigations and legal affairs. The first criminal conviction based on DNA evidence in the United States occurred in 1988. In criminal investigations, DNA fingerprints derived from evidence collected at the crime scene are compared to the DNA fingerprints of suspects. Generally, courts have accepted the reliability of DNA testing and admitted DNA test results into evidence. However, DNA fingerprinting is controversial in a number of areas: the accuracy of the results, the cost of testing, and the possible misuse of the technique.
The accuracy of DNA fingerprinting has been challenged for several reasons. First, because DNA segments rather than complete DNA strands are "fingerprinted": a DNA fingerprint may not be unique; large-scale research to confirm the uniqueness of DNA fingerprinting test results has not been conducted. In addition, DNA fingerprinting is often done in private laboratories that may not follow uniform testing standards and quality controls. Also, since human beings must interpret the test, human error could lead to false results.
DNA fingerprinting is expensive. Suspects who are unable to provide their own DNA to experts may not be able to successfully defend themselves against charges based on DNA evidence.
Widespread use of DNA testing for identification purposes may lead to the establishment of a DNA fingerprint database.
单选题The boy ahead of me is my classmate.A. at the back ofB. behindC. in front ofD. in the front of
单选题The room is
dim
and quiet.
单选题Modem adult education for large numbers of people started in the 18th and 19th centuries with the rise of the Industrial Revalution, Great economic and social changes were taking place: people were moving from rural areas to cities ; new tapes of work were being created in an expanding factory, system. These and other factors produced a need for fiwrher education and re - education of adnlts. The earliest programs of organized adult education arose in Great Britain in the 1970s. with the building of an adult school in Nottingham and a meehanies'institution in Glasgow. Benjamin Frankilin and sortie friends found the earliest adult education in the US in Philadelphia in 1727. Who can be considered to be the founder of adult education in the US?A. Washington.B. Jefferson.C. Kennedy.D. Franklin.
单选题
The Greatest Mystery of
Whales The whale is a warm-blooded,
air-breathing animal, giving birth to its young alive, sucking them—and like all
mammals, originated on land. There are many front flippers (鳍状肢), used for
steering and stability, are traces of feet. There are many {{U}} {{U}}
1 {{/U}} {{/U}}of this. Its immense strength is {{U}} {{U}}
2 {{/U}} {{/U}}into the great body of the big whales, and in fact most
of a whale's body is one gigantic muscle. The blue whale's pulling strength has
been estimated {{U}} {{U}} 3 {{/U}} {{/U}}400 horsepower. One
specimen was reported to have towed (拖) a whaling vessel for seven hours at the
{{U}} {{U}} 4 {{/U}} {{/U}}of eight knots (节).
An enraged whale will {{U}} {{U}} 5 {{/U}} {{/U}}a ship. A
famous example of this was the fate of Whaler Essex, {{U}} {{U}} 6
{{/U}} {{/U}}was sunk off the coast of South America early in the last
century. More recently, steel ships have {{U}} {{U}} 7 {{/U}}
{{/U}}their plates buckled (使弯曲) in the same way. Sperm whales (抹香鲸) were known to
seize the old-time whaleboats in their jaws and crush them. The
greatest {{U}} {{U}} 8 {{/U}} {{/U}}of whales is their diving
ability. The sperm whale dives to the bottom for his {{U}} {{U}} 9
{{/U}} {{/U}}food, the octopus (章鱼). In that search he is known to go as far
down as 3,200 feet, where the {{U}} {{U}} 10 {{/U}} {{/U}}is
1,400 pounds, to a square inch. Doing so he will {{U}} {{U}} 11
{{/U}} {{/U}}underwater long as one hour. Two special skills are involved in
this storing up enough {{U}} {{U}} 12 {{/U}} {{/U}}(all whales
are air-breathed)and tolerating the great change in pressure. Just how he does
it scientists have not {{U}} {{U}} 13 {{/U}} {{/U}}. It is
believed that some of the oxygen is stored in a special {{U}} {{U}}
14 {{/U}} {{/U}}of blood vessels, rather than just held in the lungs.
And it is believed that a special kind of oil in his head is some sort of
compensating mechanism that {{U}} {{U}} 15 {{/U}} {{/U}}adjusts
the internal pressure of his body. But since you can't bring a live whale into
the laboratory for study, no one knows just how these things work.
单选题All living organisms, {{U}}regardless{{/U}} of their unique identity, have certain logical, chemical, and physical characteristics in common.
单选题Michael is now
merely
a good friend.
单选题If Operation Migration is successful, whooping cranes will
单选题We have got to
abide by
the rules.
单选题Artificial Intelligence
For years there have been endless articles stating that scientists are on the verge of achieving artificial intelligence and that it is just around the comer. The truth is that it may be just around the corner, but they haven"t yet found the right block.
Artificial intelligence alms to build machines that can think. One immediate problem is to define thought, which is harder than you might think. The specialists in the field of artificial intelligence complain, with some justification, that anything that their machines do is dismissed as not being thought. For example, computer now plays very, very good chess.
They can"t beat the greatest players in the world, but they can beat just about anybody else. If a human being played chess at this level, he or she would certainly be considered smart. Why not a machine? The answer is that the machine doesn"t do anything clever in playing chess. It uses its blinding speed to do a brute force search of all possible moves for several moves ahead, evaluates the outcomes and picks the best. Human don"t play chess that way. They see patterns, while computers don"t.
This wooden approach to thought characterizes machine intelligence. Computers have no judgment, no common sense. So-called expert systems, one of the hottest areas in artificial intelligence aims to mimic the reasoning processes of human experts in a limited field, such as medical diagnosis or weather forecasting. There may be limited commercial applications for this sort of thing, but there is no way to make a machine that can think about anything under the sun, which a teenager can do.
The hallmark of artificial intelligence to date is that if a problem is severely restricted, a machine can achieve limited success. But when the problem is expanded to a realistic one computers fall flat on their display screens. For example, machines can understand a few words spoken individually by a speaker that they have been trained to hear. They cannot understand continuous speech using an unlimited vocabulary spoken by just any speaker.
单选题They will cut back expenditure on unnecessary items. A. stop B. continue C. shorten D. reduce
单选题She is under the {{U}}delusion{{/U}} that I'm going to give her a lot of money.
单选题By the time he was ten years old, Beniamin Oliver Davis Jr. had already decided his career would be in the air force.
单选题Sex Change Surgery Guidelines Drafted China is set to (51) its first clinical guideline on sex-change surgery, according to a notice put on the website of the Ministry of Health yesterday. The ministry is now soliciting (请求) public and professional opinions on the draft guideline. The coming guideline aims to regulate and standardize sex reassignment surgery, part of a treatment for gender identity disorder in transsexuals (变性者). Experts (52) nearly 2,000 Chinese have undergone sex-change surgery while 100,000 to 400,000 are still considering it. However, no official number is available. In the draft, the MOH sets (53) criteria for both surgical candidates and medical institutions. Candidates for the surgery must be older than 20 and single, the draft guideline said. They are also required to prove a persistent desire for a sex change, to live for at least five consecutive years full-time in the new gender role, and to engage (54) mental therapy for at least one year. Before surgery can take place, a candidate must receive a recommendation for the operation from a (55) after an appropriate series of therapy sessions. Also, several legal requirements (56) be met before the procedure. The candidate must provide proof from police that he or she has does not have any criminal offenses in the past. Police must also agree to change the sex status on the identity card of the (57) receiver before the operation can, take (58) . The advent of such a guideline (59) to show that the government is concerned (60) the needs of a relatively small (61) of people who want to change sex. But doctors also warn that all stakeholders (利益相关者) , including the hospital and prospective receivers, should be highly cautious about this surgery. The operation is more than a medical procedure due (62) its huge social and legal consequences. Doctors should make it clear to those (63) sex-change surgeries that the option always remains to continue to live in the original role. The guideline requires surgeons to tell patients about other options (64) hormone therapy. They are also required to explain the risks involved, and underlying social barriers including discrimination, and administrative recognition and approval. For the candidates, the surgery itself is not the big issue (65) the long run. The real issue is the kind of life he or she will have to lead afterward.
单选题At first the man demanded one thousand dollars for the used car but eventually he had to {{U}}settle for{{/U}} half that amount.
单选题By providing legal representation, the American Civil Liberties Union works to defend citizens against {{U}}breaches{{/U}} of their civil rights.
单选题阅读下面的短文，文中有15处空白，每处空白给出4个选项，请根据短文的内容从4个选项中选择1个最佳答案。
The Greatest Mystery of
Whales The whale is a mammal(哺乳动物) warm-blooded,
air-breathing, giving birth to its young alive, sucking them—and, like all
mammals, originated on land. There are many signs of this. {{U}}
(51) {{/U}} front flippers (鳍肢), used for steering and stability, are
traces of feet. Immense strength is built into the great body of
the big whales, and in fact most of a whale's body is one gigantic muscle. The
blue whale's pulling {{U}}(52) {{/U}} has been estimated at 400
horsepower. One specimen was reported to have {{U}}(53) {{/U}} a whaling
vessel for seven hours at the {{U}}(54) {{/U}} of eight knots.
An enraged whale will attack a ship. A famous {{U}}(55) {{/U}} of
this was the fate of whaler Essex, which was sunk {{U}}(56) {{/U}} the
coast of South America early in the last century. More recently, steel ships
have had their plates buckled (扭曲变形) in the same way. Sperm whales were known to
{{U}}(57) {{/U}} the old-time whaleboats in their jaws and crush
them. The greatest mystery of whales is their diving ability.
The sperm whale can {{U}}(58) {{/U}} the bottom for his favorite food,
the octopus (章鱼). {{U}}(59) {{/U}} that search he is known to go as far
down as 3,200 feet, where the pressure is 1,400 pounds, to the square inch.
Doing {{U}}(60) {{/U}} he will remain submerged (水下的) as long as one
hour. Two feats (绝技) are involved in this: storing up enough {{U}}(61)
{{/U}} (all whales are air-breathed) and withstanding the great change in
pressure. Just {{U}}(62) {{/U}} he does it scientists have not
determined. It is believed that some of the oxygen is stored in a special system
of blood vessels, rather than just held in the lungs. And {{U}}(63)
{{/U}} is believed that a special kind of oil in his head is some sort of
compensating mechanism that automatically adjusts the internal pressure of his
body. But {{U}}(64) {{/U}} you can't bring a live whale into the
laboratory for study, no one {{U}}(65) {{/U}} just how these things
work.
单选题Spielberg says he makes movies for
单选题If I made a mistake, I will try to remedy it. A. clarify B. diagnose C. evaporate D. correct