题目内容
听力原文： Do you have trouble sleeping at night？ Then maybe this is for you. When you worry about meeting sleep and twisting around, trying to find a comfortable position, you're probably only making matters worse. What happens is that your heart rate actually increases, making it more difficult to relax. You may also have some bad habits that contribute to the problem. Do you rest frequently during the day？ Do you get virtually no exercise, or do you exercise strenuously late in the day？ Do you think about sleep a lot or sleep late on weekends？ Any of these facts might be leading to your insomnia by disrupting your body's natural rhythm. What should you do then on those sleepless nights？ Don't bother with sleeping pills; they can actually cause worse insomnia, later. The best thing to do is to drink milk or eat cheese or tuna fish. They are all rich in the amino acid that helps produce in the brain a neural transmitter that induces sleep. This neural transmitter will help you relax, and you'll be on the way to get a good night's sleep. Until tomorrow's broadcast, this has been another series "Hint for Good Health" by Doctor Handison.
We can learn from the passage that when twisting around,______.
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SECTION A CONVERSATIONS
Directions: In this section you will hear several conversations. Listen to the conversations carefully and then answer the questions that follow.
听力原文：W: I just read a curious fact. Did you know that people who spend less than ten minutes in a drugstore are five times more likely to make a purchase than those who spend half an hour there？
M: I saw that article, too. But I think, if someone runs into a drugstore for ten minutes, it's usually to make a specific purchase.
W: And someone .who spends more time there may be just looking.
M: Exactly. Haven't you ever gone into a store thinking that you'd buy something, and then talk yourself out of it？
W: Yes, I have. Especially when I thought I could get it for less elsewhere, or I really didn't need it after all.
M: Exactly. But if you run in to buy something specific and have very little time, you pick it up, pay for it immediately and then leave.
W: That's true. Maybe we should learn a lesson from that. Take your time and you'll spend less money.
M: I doubt if that would be true in all stores, though. In a department store, for instance, you may see a sweater or something you never intended to buy and buy it because you have time to look around.
People are more likely to make a purchase ______.
Where is the talk most probably being given？
The concept is to develop vehicles that can run on a virtually limitless element hydrogen which when burned does not produce damaging fumes, but instead a bit of water vapour. The concept can solve two problems at once. First, it is a hedge for that day in the 21st century when hydrocarbon fuels run out, a prospect of no minor concern for the automotive industry.
Beyond that, the increasingly dire warnings by environmental scientists about the "greenhouse effect" in atomosphere caused by carbon dioxide exhausts adds urgency to the quest for a fuel that is less damaging to the environment.
Of course, there is a hitch to hydrogen, both carmakers admit :though the know -how to run vehicles on nature’ slightest element is already available, hydrogen is far from being cost competitive compared to hydrocarbon fuels, and further refinements hydrogen -propulsion technology will be required. But what we are discussing today is the technology of the year 2020.
But after several year's research Daimler and BMW engineers, in collaboration with other companies and research institutes in West Germany, independently have been tackling the technological and cost feasibility problems to be overcome in hydrogen fuel application.
In addition to the two concerns of technology and economic feasibility, the carmakers say, there is the issue of safety. The spectacular explosion of the dirigible. Hindenburg in 1937 immediately comes to mind, and skeptics wonder what the German autobahn would look like in one of the hundred - car pileups that routinely happen every winter if all the cars and tanks loaded with hydrogen.
A BMW engineer, Friedich Fickel, says that hydrogen is seen as less risky than gasoline. When leaked, hydrogen rises quickly up to the atmosphere, reducing the potential of explosion, whereas gasoline fumes linger close to the ground before dispersing. Still, both Daimler and BMW report that a considerable part of their development efforts are aimed at safe, lead - free storage of hydrogen fuel.
The related question is what is the best method of storage. By now ,the tests by both carmakers have all but eliminated using hydrogen in gas form. As a gas it takes up about 14 times the space of liquid hydrogen and as much as 30 percent can be lost by leakege unless the tanks are perfectly sealed.
Two other storage methods hold more promise. One is in liquid form, and the other in the form. of metal hydrides. In the latter, hydrogen if mixed with a metal alloy ,a process whereby the gas molecules are stored within the metal's molecular structure.
Which of the following is the characteristic of hydrogen？
Tripod is ______.
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