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提问人:网友wanghu9999 发布时间:2022-01-06
[主观题]

What operation on relations R and S produces the relation shown below? { tuple | tuple∈R ∨

tuple∈S} ()

A.union

B.difference

C.intersection

D.division

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更多“What operation on relations R and S produces the relation shown below? { tuple | tuple∈R ∨”相关的问题
第1题
听力原文:Hi, Jim! You look pretty good today. Everybody at the office says hello. We're al
l pulling for you to pull through this operation and get back to work at soon as you can.

What's wrong with Jim?

A.He's going through an operation.

B.He's getting sick.

C.He's had an accident.

D.He looks good today.

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第2题
听力原文:W: The doctor will see you in a minute, Mr. Lewis. While you're waiting, you can
answer some questions.

M: But, nurse, you don't understand. I'm very healthy. I only want to see the doctor about…I mean, I want to pay the doctor for my wife's operation last month.

Q: What did the man want to do?

(19)

A.He wanted to ask the doctor some questions.

B.He wanted to see the doctor.

C.He wanted to pay the doctor.

D.He wanted to see the nurse.

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第3题
Listen to the dialogue. Then write the words you h...

Listen to the dialogue. Then write the words you hear in the blanks. (I=Interviewer, IT= Indira Thambiah) I. Argos sells goods in its ____1_____ stores and online. How do you run these operations successfully _____2_______? IT. The key to our success is that we treat the customer as a single _____3____, and we don't treat customers as online customers or store customers. Our experience shows that customers will sometimes buy online, sometimes order on the telephone and sometimes go into the stores to pick up goods. So we need to understand what our customers want at any one time or what our customers want depending on the product that they' re buying, and serve those customers in the most _____4______ way. In terms of our operation, our operations are fully ____5____. The prices that we show on the website are identical to the prices that you would pay in the store. You can call up a call center and enquire about an order that you, you placed through any channel, whether that's the store, the website or the telephone. And if you buy something from the website and you don't like what you've got you can return that item to a store. So running a ___6___ operation is the key to our success. We don't run operations side by side; we run a truly integrated multichannel offer. I. What do you think are the keys to success in online selling? IT. I think the, the most important thing is to understand that customers use websites for lots of different reasons. Some people are coming to a website to actually buy something on that day; a lot of other people are coming to a website to ____7____ information either about a product or about the retailer, and the key to selling online is to understand or recognize what the customer wants when they're on your website and try and provide that information. So the keys for us are providing good _____8_____ and good information - technical information on all of the products that we sell; being very clear about the price of the product and any _____9_____ that are running alongside those products; being very clear to the customer about what the ____10____ options are for each individual product; and then, allowing them to find all of that information and then buy once they’re ready.

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第4题
PART CDirections: You will hear three dialogues or monologues. Before listening to each on

PART C

Directions: You will hear three dialogues or monologues. Before listening to each one, you will have 5 seconds to read each of the questions which accompany it. While listening, answer each question by choosing A, B, C or D. After listening, you will have 10 seconds to check your answer to each question. You will hear each piece ONLY ONCE.

听力原文:W: What' s the advantage of using nuclear power in the generation of electricity?

M: In an advanced reactor, as much electricity can be made from one ton of enriched uranium fuel as from 75, 000 tons of coal.

W: Then you need only a few lorry loads of fuel at a nuclear power station instead of many trains of coal.

M: Exactly!

W: With coal you have a residue of ash. What about the used fuel from a nuclear-powered station? W: Well, being radioactive, it can't be left lying around.

M: So how do you dispose of it?

M: It's loaded into thick steel flasks each weighing 45 tons. They' re dispatched to the United Kingdom Atomic Energy Authority for reprocessing.

W: So there's little actual wastage?

M: But that doesn't eliminate cost. The reprocessing isn't done for nothing.

W: But electricity from a nuclear-powered station is cheaper than from a coal-fired plant, isn't it? M: Well, the cost of operation of nuclear stations is only half the cost of even the least expensive coal-fired stations. And later on the figures will show an even greater advantage for nuclear energy.

W: But don't nuclear stations cost more to build?

M: Yes, they do. However, their cheaper running gains more than offsets the construction costs.

W: And aren't the nuclear stations cleaner in operation?

M: Yes, and they' re better looking than conventional stations and can be built in places unsuitable for conventional plants. In most cases, they are safe.

What are the two speakers talking about?

A.The benefits of nuclear weapons.

B.The environmental pollution caused by nuclear-powered stations.

C.The disadvantages of used fuel.

D.The advantages of nuclear-powered stations.

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第5题
听力原文:W: I wonder if there's a difference in work attitude--working in a small company
or working for a big company.

M: Yes, sure there're differences. I guess that you're more...uh...conscious of time when you work for a big company.

W: What do you mean?

M: Well, you get this eight-to-five attitude. You know, five o'clock rolls around, and you get up and go home. And now it's your time.

W: Uhm.

M: Uh... well, when in a small company, you are personally involved and do things because you want to. In the big corporation, you are not as much in control of the exact environment that you are in.

W: There's something sort of...uh...impersonal about a big company to a lot of people.

M: Well, it's impersonal in that...uh...probably just a small percentage of the employees know the top management.

W: Hmm...

M: And none of them probably have ever seen the president of the company. So, from that sense, it's impersonal.

W: Do you operate on a first-name basis?

M: In our company, almost everybody deals on a first-name basis. When I see the president, I call him by his first name. And everybody does so.

W: Well, it sounds like you're saying that there's a certain amount of pride and satisfaction in doing the job.

M: Indeed! And in a small company, I think the individual would have a greater sense of the company's goal.

W: Sort of group spirit or something?

M: You may say that. People know exactly what the product is, and what they're performing and why they are performing it. In a large company, people get further away from the end product.

W: In that case, it's not an identification with the primary goal of the company.

M: That's exactly what I mean.

(27)

A.The differences in work attitudes of employees in big companies and small companies.

B.The management styles of executives in big companies and small companies.

C.The percentage of employees involved in top management in big companies and small companies.

D.The operation on a first-name basis in big companies and small companies.

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第6题
听力原文:Mr Richards worked in a shop which sold, cleaned and repaired hearing aids. One d

听力原文: Mr Richards worked in a shop which sold, cleaned and repaired hearing aids. One day an old gentleman entered and put one down in front of him without saying a word. "What's the matter with it?" Mr Richards said. The man did not answer. Of course Mr Richards thought that the man must be deaf and that his hearing aid must be faulty, so he said again, more loudly, "what's wrong with your hearing aid, sir?" Again the man said nothing, so Mr Richards shouted his question again as loudly as he could.

The man then took a pen and piece of paper and wrote: "It isn't necessary to shout when you're speaking to me. My ears are as good as yours. This hearing aid is my wife's, not mine. I've jut had a throat operation, and my problem is not that I can't hear, but that I can't speak."

(23)

A.He wanted to buy a hearing-aid.

B.He wanted to have a hearing-aid repaired.

C.He wanted to get a pen and a piece of paper.

D.He wanted to solve his own problem.

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第7题
Spare a Kidney? It is no longer unusual for a spouse or relative to donate a kidney to a l

Spare a Kidney?

It is no longer unusual for a spouse or relative to donate a kidney to a loved one, but the number of Americans who have given a kidney to a friend, a co-worker or even a complete stranger has risen sharply from 68 in 1994 to 176 in 1998.

There are many reasons. First, it's possible to live a normal life with only one kidney. (The remaining kidney enlarges to make up most of the difference.) in addition a kidney from a live donor lasts longer than a kidney taken from someone who has died suddenly. But the biggest change in the past few years is that transplant surgeons have started using laparoscopic techniques to remove the donor kidney through a much smaller incision, and this can cut recovery time for the donor from six weeks to four weeks.

Just because you can do something, however, it doesn't mean you should. Donating a kidney means undergoing an operation that carries some risk. You could argue that you may be helping to save a life, but you certainly can't pretend that you're better off with one kidney instead of two.

So, what are the risks? "As with any major operation, there is a chance of dying, of reoperation due to bleeding, of infection, of vein clots in the legs or a hernia at the incision," says Dr. Arthur Matas, director of the renal-transplant program at the University of Minnesota Medical Center in Minneapolis. Even laparoscopy, a relatively new technique for kidney donation, is not risk-free. Doctors estimate that chances of dying from the procedure are about 3 in 10,000.

There's no money to be made; selling an organ is illegal. But the recipient's insurance normally covers your operation and immediate aftercare. Your costs can include hotel bills, lost pay during recovery or possible future disability.

Although transplant centers must evaluate any potential donor's suitability, it never hurts to have an independent opinion. The most common contraindications are heart disease, diabetes and high blood pressure.

Never let anyone, not even a close relative, pressure you into giving up an organ -- no matter if you're healthy. "There's often the feeling that you're not a good friend, father, mother if you don't do this," says Arthur Caplan, director of the University of Pennsylvania's Center for Bioethics. Some transplant centers will invent a "medical problem" on behalf of those who are reluctant to donate but feel they can't say no.

From 1994 to 1998 the number of Americans who had donated a kidney reached 244.

A.Right

B.Wrong

C.Not Mentioned

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第8题
Spare a Kidney?It is no longer unusual for a spouse or relative to donate a kidney t0 a lo

Spare a Kidney?

It is no longer unusual for a spouse or relative to donate a kidney t0 a loved one, but the number of Americans who have given a kidney to a friend, a co-worker or even a complete stranger has risen sharply from 68 in 1994 to 176 in 1998.

There are many reasons. First, it's possible to live a normal life with only one kidney. (The remaining kidney enlarges to make up most of the difference.)In addition a kidney from a live donor lasts longer than a kidney taken from someone who has died suddenly. But the biggest change in the past few years is that transplant surgeons have started using 1aparoscopic techniques to remove the donor kidney through a much smaller incision, and this can cut recovery time for the donor from six weeks to four weeks.

Just because you do something, however, it doesn't mean you should, Donating a kidney means under- going an operation that carries some risk. You could argue that you may be helping to save a life, but you certainly can't pretend that you're better off with one kidney instead of two.

So, what are the risks? “As with any major operation, there is a chance of dying, of reoperation due to bleeding,Of infection,Of vein clots in the legs Or a hernia at the incision,”says Dr.Arthur Matas,director of the renal-transplant program at the university of Minnesota Medical Center in Minneapolis. Even laparoscopy, a relatively new technique for kidney donation, is not risk-free. Doctors estimate that chances of dying from the procedure are about 3 in 10,000.

There's no money to be made; selling an organ is illegal. But the recipient's insurance normally covers your operation and immediate aftercare. Your costs can include hotel bills, lost pay during recovery or possible future disability.

Although transplant centers must evaluate any potential donor's suitability, it never hurts to have an independent opinion. The most common contraindications(禁忌征候)are heart disease, diabetes and high blood pressure.

Never let anyone, not even a close relative, pressure you into giving up an organ—no matter if you're healthy. "There's often the feeling that you're not a good friend, father, mother if you don't do this," says Arthus Caplan, director of the University of Pennsylvania's center for Bioethics. Some transplant centers will invent a "medical problem" on behalf of those who are reluctant to donate but feel they can't say no.

16. From 1994 to 1998 the number of Americans who had donated a kidney reached 2419.

A.Right

B.Wrong

C.Not mentioned

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第9题
听力原文:W: Hi, Paul, are you ready for your Speech Club presentation this evening?M: Yeah

听力原文:W: Hi, Paul, are you ready for your Speech Club presentation this evening?

M: Yeah, I' m going to discuss robots.

W: Robots? You mean those machines that walk and talk like in the movies?

M: No, industrial robots like those used in the automobile and electronic industries.

W: I saw an article about that kind of robot the other day. There were pictures of robots welding cars, but they certainly didn’t look the way I thought robots should look.

M: The robots we usually imagine are made up in science fiction. In industry, robots are designed to do a specific set of operations, such as welding car frames. They are rarely built to resemble humans.

W: Actually, all they need is a kind of brain to give signals, and a mechanism, such as an arm, to carry out instructions, right?

M: Right. Tiny computers become the brain of these robots. The computer sends signals, in the form. of electronical impulses, and move an arm and a claw. The claw is the hand that does particular kinds of work.

W: OK. But we' ye had machines on assembly lines doing work for people for years. That’s what started the industrial revolution, remember?

M: But each of those machines can only perform. a single operation and it takes months to modify them. The new industrial robots can each do a number of tasks. And it’s easy to reprogram them to perform. totally different operations. That’s one reason why they're becoming so popular.

W: They increase productivity too, don't they? I read that even though they're still quite expensive, they often cost less per year than a worker doing the same job. I imagine robots will be used more and more.

M: Exactly. So now that you know all about the next industrial revolution, you don’t have to come to Speech Club tonight.

What kind of robots does the man refer to?

A.Agricultural robots.

B.Industrial robots.

C.Computers.

D.Electrical robots.

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第10题
听力原文:W: Hi, Paul, are you ready for your Speech Club presentation this evening?M: Yeah

听力原文:W: Hi, Paul, are you ready for your Speech Club presentation this evening?

M: Yeah, I'm going to discuss robots.

W: Robots? You mean those machines that walk and talk like in the movies?

M: No, industrial robots like those used in the automobile and electronic industries.

W: I saw an article about that kind of robots the other day. There were pictures of robots welding cars, but

they certainly didn't look the way I thought robots should look.

M: The robots we usually imagine are made up in science fiction. In industry, robots are designed to do a specific set of operations, such as welding car frames. They are rarely built to resemble humans.

W: Actually, all they need is a kind of brain to give signals, and a mechanism, such as an arm, to carry out instructions, right?

M: Right. Tiny computers become the brain of these robots. The computer sends signals, in the form. of electronic impulses, to move an arm and a claw. The claw is the hand that does particular kinds of work.

W: OK. But we've had machines on assembly lines doing work for people for years. That's what started the industrial revolution, remember?

M: But each of those machines can only perform. a single operation and it takes months to modify them. The new industrial robots can each do a number of tasks. And it's easy to reprogram them to perform. totally different operations. That's one reason why they're becoming so popular.

What kind of robots does the man refer to?

A.Agricultural robots.

B.Industrial robots.

C.Computers.

D.Electrical robots.

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第11题
In a country that defines itself by ideals, not by shared blood, who should be allowed to
come, work and live here? In the wake of the Sept. 11 attacks these questions have never seemed more pressing.

On Dec. 11, 2001, as part of the effort to increase homeland security, federal and local authorities in 14 states staged "Operation Safe Travel"--raids on airports to arrest employees with false identification (身份证明). In Salt Lake City there were 69 arrests. But those captured were anything but terrorists, most of them illegal immigrants from Central or South America. Authorities said the undocumented workers' illegal status made them open to blackmail(讹诈) by terrorists.

Many immigrants in Salt Lake City were angered by the arrests and said they felt as if they were being treated like disposable goods.

Mayor Anderson said those feelings were justified to a certain extent. "We're saying we want you to work in these places, we're going to look the other way in terms of what our laws are, and then when it's convenient for us, or when we can try to make a point in terms of national security, especially after Sept. 11, then you're disposable. There are whole families being uprooted for all of the wrong reasons," Anderson said.

If Sept. 11 had never happened, the airport workers would not have been arrested and could have gone on quietly living in America, probably indefinitely. And Castro, a manager at a Ben & Jerry's ice cream shop at the airport, had been working 10 years with the same false Social Security card when she was arrested in the December airport raid. Now she and her family are living under the threat of deportation(驱逐出境). Castro's case is currently waiting to be settled. While she awaits the outcome, the government has granted her permission to work here and she has returned to her job at Ben & Jerry's.

According to the author, the United States claimed to be a nation ______.

A.composed of people having different values

B.encouraging individual pursuits

C.sharing common interests

D.founded on shared ideals

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