根据材料回答下列各题: The most frightening words in the English language are, "Our comput
A.When the Computer Is Down
B.The Most Frightening Words
C.The Computer of the Airport
D.Asking the Computer
A.When the Computer Is Down
B.The Most Frightening Words
C.The Computer of the Airport
D.Asking the Computer
A.Eat it in the early morning.
B.Include various nutrients.
C.Eat something low in calories.
D.Eat much for the whole morning.
A、warehouse
B、head office
C、subsidiary
D、branch
Each advance in microscopic technique has provided scientists with new perspectives on the function of living organisms and the nature of matter itself. The invention of the visible-light microscope late in the sixteenth century introduced a previously unknown realm of single celled plants and animals. In the twentieth century, electron microscope have provided direct views of viruses and minuscule surface structures. Now another type of microscope, one that utilizes X rays rather than light or electrons, offers a different way of examining tiny de tails; it should extend human perception still farther into the natural world.
The dream of building an X-ray microscope dates to 1895; its development, however, was virtually halted in the 1940's because the development of the electron microscope was progressing rapidly. During the 1940's, electron microscopes routinely achieved resolution better than that possible with a visible-light microscope, while the performance of X-ray microscopes resisted improvement. In recent years, however, interest in X-ray microscopes has revived, largely because of advances such as the development of new sources of X-ray illumination. As a result, the brightness available today is millions, of times that of X-ray tubes, which, for most of the century, were the only avail able sources of soft X-rays.
The new X-ray microscopes considerably improve on the resolution provided by optical microscopes. They can also be used to map the distribution of certain chemical elements. Some can form. pictures in extremely short times; others hold the promise of special capabilities such as three-dimensional imaging. Unlike conventional electron microscopy, X-ray microscopy enables specimens to be kept in air and in water, which means that biological samples can be studied under conditions similar to their natural state. The illumination used, so-called soft X rays in the wavelength range of twenty to forty angstroms (an angstrom is one ten-billionth of a meter), is also sufficiently penetrating to, image intact biological cells in many cases. Because of the wavelength of the X rays used, soft X-ray microscopes will never match the highest resolution possible with electron microscopes. Rather, their special properties will make possible investigations that will complement those performed with light-and-electron-based instruments.
What does the passage mainly discuss?
A.The detail seen through a microscope.
B.Sources of illumination for microscopes.
C.A new kind of microscope.
D.Outdated microscopic techniques.
A.About 18 months.
B.About 21 months.
C.About 24 months.
D.About 12 months,
A.Their children.
B.Their niece and nephew.
C.Their friend s children.
D.Their neighbor s kids.
A.He has lost his ticket.
B.He is expecting a ticket.
C.He went out to buy a ticket.
D.He collectstickets.
根据材料回答下列各题: In Britain, people have different attitudes to the police. Most people generally ______26______themand the job they do-although there are certain people who do not believe that the police______ 27______have the power that do. What does a policeman actually do? It is not______28______job to describe. After all, a policeman hasa number of jobs in ______ 29______ . In Britain, he might be in the Traffic Police and ______ 30 ______most of histime______ 31 ______up and down main roads and motorways. A traffic policeman has to keep the traffic ______32______and help when there is an accident. A policeman has to help keep the ______ 33______ , too. If there is a fight or some other disturbance,we ______ 34 ______the police to come and restore order. And they often have to ______ 35 ______situation at greatrisk to their own ______ 36______. We expect the police to solve crimes, of course, so an ordinary policeman,______ 37 ______ he is not a detective, will often have to help ______ 38 ______and arrest criminals. And ______ 39 ______ do we call when there is an emergency-an air crash, a ______ 40 ______ , a road accident,or a robbery? We call the police.41a policeman has to be42to face any unpleasant e-mergency that may happen in the ______ 43 ______world. The police do an absolutely necessary job, they do it ______ 44 ______ well and I support them, but I do not envy policemen, I do not think that I could ______ 45 ______do the job of a policeman.
A.dislike
B.join
C.appreciate
D.admire
为了保护您的账号安全,请在“简答题”公众号进行验证,点击“官网服务”-“账号验证”后输入验证码“”完成验证,验证成功后方可继续查看答案!