Many superstitious people are afraid of black cats. They believe that black cats have a strange power. If a black cat crosses their path, they think they will have bad luck.Black cats haven’t always had such a bad reputation. Long ago, the Egyptians thought that black cats were holy animals. They even worshipped them. Pasht was an Egyptian goddess who had a woman’s body and a cat’s head. Because the Egyptians had so much respect for black cats, they often buried the sacred creatures with great ceremony. Mummies of cats have often been found in ancient cemetery ruins. To keep the cats company after they died, mice were sometimes buried beside them.Feelings about black cats have always been strong. People have thought they were either very good or very bad. The people of Europe, in the Middle Ages, believed black cats were the evil friends of witches and the Devil. Witches were said to have the power to change themselves into black cats. People believed that you could not tell whether a black cat was just a cat, or whether it was a witch disguising herself as she plotted some evil scheme. The brain of a black cat was thought to be a main ingredient in witch’s brew.Unlike their ancestors of the Middle Ages, Englishmen today consider black cats to be good luck charms. Fishermen’s wives often keep a black cat around so that their husbands will be protected when they are out at sea. The Egyptian goddess Pasht had a()
A. woman’s head and a cat’s body
B. woman’s head and a lion’s body
C. cat’s head and a man’s body
D. woman’s body and a cat’s head
If you are like most people, your intelligence varies from season to season. You are probably a lot sharper in the spring than you are at any other time of the year. A noted scientist, Ellsworth Huntington (1876-1947), concluded from other men’s work and his own among peoples in different climates that climate and temperature have a definite effect on our mental abilities.He found that cool weather is much more favorable for creative thinking than is summer heat. This does not mean that all people are less intelligent in the summer than they are during the rest of the year. It does mean, however, that the mental abilities of large numbers of people tend to be lowest in the summer.Spring appears to be the best period of the year for thinking. One reason may be that in the spring man’s mental abilities are affected by the same factors that bring about great changes in all nature.Fall is the next-best season, then winter. As for summer, it seems to be a good time to take a long vacation from thinking! One possible reason why spring is the best season for thinking is that ()
A. all nature, including man, is growing then
B. it lasts longer than the other seasons
C. it is not too warm and not too cold
D. both B and C
Rabies is an ordinarily infectious disease of the central nervous system, caused by a virus and, as a rule, spread chiefly by domestic dogs and wild flesh-eating animals. Man and all warm-blooded animals are susceptible to rabies. The people of ancient Egypt, Greece and Rome ascribed rabies to evil spirits because ordinarily gently and friendly animals suddenly became vicious and violent without evident cause and, after a period of maniacal behaviour, became paralysed and died. Experiments carried out in Europe in the early nineteenth century of injecting saliva from a rabid dog into a normal dog proved that the disease was infectious. Preventive steps, such as the destruction of stray dogs, were taken and by 1826 the disease was permanently eliminated in Norway, Sweden and Denmark. Though urban centres on the continent of Europe were cleared several times during the nineteenth century, they soon became reinfected since rabies was uncontrolled among wild animals. During the early stages of the disease, a rabid animal is most dangerous because it appears normal and friendly, but it will bite at the slightest provocation. The virus is present in the salivary glands(腺) and passes into the saliva so that the bite of the infected animal introduces the virus into a fresh wound. If no action is taken, the virus may become established in the central nervous system and finally attack the brain. The incubation(潜伏期) period varies from ten days to eight months or more, and the disease develops more quickly the nearer to the brain the wound is. Most infected dogs become restless, nervous, and irritable and vicious, then depressed and paralysed. With this type of rabies, the dog’s death is inevitable and usually occurs within three to five days after the onset of the symptoms. Anti-rabies vaccine(疫苗) is widely used nowadays in two ways. Dogs may be given three-year protection against the disease by one powerful injection, while persons who have been bitten by rabid animals are given a course of daily injections over a week or ten days. The mortality rate from all types of bites from rabid animals has dropped from 9% to 0.5%. In rare cases, the vaccine will not prevent rabies in human beings because the virus produces the disease before the person’s body has time to build up enough resistance. Because of this, immediate vaccination is essential for anyone bitten by an animal observed acting strangely and the animal should be captured circumspectly, and examined professionally or destroyed. How does the virus of a rabid animal infect man or other animals
A. The virus is infected into their bodies.
B. The bite of the infected animals passes the virus presenting the saliva to others.
C. The virus has established in their central nervous systems for several years.
D. The virus infect them by some infectious diseases.
CPU在执行一段程序时,在Cache中完成的存取次数是950次,在主存中完成的存取次数是50次,已知Cache的存取周期是40us,主存的存取周期是200us,求Cache/主存系统的效率和平均访问时间。