单选题His friend unexpectedly dropped in .

单选题We are worried about this fluid situation full with uncertainty.

单选题The passage indicates that ancient treatments for injury and disease were

单选题I can't make it because of a previous engagement.A. primaryB. priorC. temporalD. primitive

单选题There is no doubt that we are living in a period of enormous population growth. In the past, it (51) thousands of years for the world's population to double in size. (52) today there are more people having families and fewer deaths from diseases. As(a) (53) , the population doubles in only 35 years. A(n) (54) supply of food is only one of the human needs that must be (55) . Overcrowding has a highly undesirable effect on life. For example, if every available piece of land were used for producing food, it would be very difficult to (56) proper housing for people, as would health care and recreation. (57) these reasons, more governments are helping families to understand the problems of (58) population. They give 'family planning' advice to families that request it. Such families can plan to have the number of children they want, at times when they are best able to care (59) children and give them a good start in life. (60) rice that have been highly successful in Asia and in (61) African countries. The significance of such work was recognized by the awarding of the 1970 Nobel Peace Prize (62) one of the plant breeders of the 'green revolution'. (63) to grow well, the improved seeds need large (64) of fertilizer and water, which are not always (65) . Many fertilizers are made up of petroleum, and higher prices for oil have resulted in smaller supplies of fertilizers.

单选题A red flag was placed there as a token of danger.

单选题 Food and Cancer Medical experts have suspected for many years that there is a strong link between what a person eats and cancer. They say a new study provides the first evidence that vitamins could reduce a person's chance of developing cancer. A team of Chinese and American scientists did the study. They are from American National Cancer Institute and the Cancer Institute of the Chinese Academy of Medical Sciences in Beijing. The Journal of the National Cancer Institute published the results of the study. About thirty thousand people between the ages of 40 to 69 took part in the study. They were from the northern central Chinese area of Linxian. Most of them took vitamins and minerals every day for five years. Linxian was chosen because the people there have an extremely high rate of cancer of stomach and esophagus. Researchers believe that fungus and molds in local foods may be partly responsible for the high cancer rate. Researchers divided those into eight groups. Seven of the groups received different mixtures of vitamins and minerals daily. The amounts of the vitamins and minerals were 1 to 2 times greater than what American health officials say is needed. The eighth group received sugar pills that had no effect. Those who seemed to gain the most received a mixture of a form of vitamin A called β-carotene, vitamin E and the mineral selenium. The vitamin and mineral are believed to prevent damage to cells caused by cancer-causing substances. Researchers reported a 13 percent drop in cancer rates in those who took β-carotene, vitamin E and selenium. They also found a 10 percent drop in the number of deaths caused by strokes from bursting blood vessels. Scientists warn that it is too soon to know if the effect would be the same among people in other countries. They note that the people in Linxian eat foods that lack necessary vitamins and minerals. Chinese officials will continue to record the health records of the people in Linxian for many years. For now officials reportedly are considering using the .results of the study. They want to find a way to improve the health of people in Linxian and other small towns in China.

单选题Manyscientists have been probing psychologicalproblems.

单选题Students have to obey the rules in the school.A. reply toB. apply forC. abide withD. comply with

单选题______ in a simple style, the book clearly describes the author' s childhood experiences in a small town.A. WritingB. To be writtenC. Being writtenD. Written

单选题The Californian redwoods, the tallest trees in the world, are known for their ability to withstand fire, insects and disease.A. bearB. resistC. attackD. defend

单选题Plant Gas Scientists have been studying natural sources of methane for decades but hadn"t regarded plants as a producer, notes Frank Keppler, a geochemist at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. Now Keppler and his colleagues find that plants, from grasses to trees, may also be sources of the greenhouse gas. This is really surprising, because most scientists assumed that methane production requires an oxygen- free environment. Previously, researchers had thought that it was impossible for plants to make significant amounts of the gas. They had assumed that, microbes need to be in environments without oxygen to produce methane. Methane is a greenhouse gas, like carbon dioxide. Gases such as methane and carbon dioxide trap heat in Earth"s atmosphere and contribute to global warming. In its experiments, Keppler"s team used sealed chambers that contained the same concentration of oxygen that Earth"s atmosphere has. They measured the amounts of methane that were released by both living plants and dried plant material, such as fallen leaves. With the dried plants, the researchers took measurement at temperatures ranging from 30℃ to 70℃. At 30℃, they found, a gram of dried plant material released up to 3 nanograms of methane per hour. (One nanogram is a billionth of a gram.) With every 10-degree rise in temperature, the amount of methane released each hour roughly doubled. Living plants growing at their normal temperatures released as much as 370 nanograms of methane per gram of plant tissue per hour. Methane emissions tripled when living and dead plant was exposed to sunlight. Because there was plenty of oxygen available, it"s unlikely that the types of bacteria that normally make methane were involved. Experiments on plants that were grown in water rather than soil also resulted in methane emissions. That"s another strong sign that the gas came from the plants and not soil microbes. The new finding is an "interesting observation", says Jennifer Y. King, a biogeochemist at the University of Minnesota in St. Paul. Because some types of soil microbes consume methane, they may prevent plant-produced methane from reaching the atmosphere. Field tests will be needed to assess the plant"s influence, she notes.

单选题 U.S. States Do Poorly in Women's Health Not a single U.S. state meets basic federal goals for women's health, and the nation as a whole fails except in two areas—mammograms (乳腺X光照片) and dental (牙齿的) check-ups—researchers said on Thursday. Millions of women lack health insurance, and states make it difficult to enroll (加入) in Medicaid, the state-federal health insurance plan for the poor, according to the report. And few states are doing anywhere near enough to help women quit smoking—the leading cause of death in the United States. "The nation as a whole and the individual states fall short of meeting national goals," reads the report, put together by the National Women's Law Center (NWLC) and the Oregon Health & Science University. "These health goals provide a road map for assessing the status of women's health." Of 27 measures examined by the group, from screening for diseases to actually treating them, the nation passes on only two, the researchers said. "The nation is so far from the health goals that it receives an overall grade of 'unsatisfactory'," they wrote. The problem seems to be a lack among states of an overall plan for health in general, the NWLC said. "State policy makers' piecemeal (一件一件做的) approach to our health care crisis has resulted in a complex and ineffective system that fails to meet the health care needs of women," Judy Waxman, NWLC Vice President for Health, said in a statement. "Lawmakers need to take a comprehensive, long-term approach to meeting women's health needs and tackle this serious problem that troubles so many families. "

单选题Bacteria Bacteria are extremely small living things. While we measure our own sizes in inches or centimeters, bacterial size is measured in microns. One micron is a thousand of a millimeter: a pinhead is about a millimeter across. Rod-shaped bacteria are usually from two to four microns long, while rounded ones are generally one micron in diameter. Thus if you enlarged a rounded bacterium a thousand times, it would be just about the size of a pinhead. An adult human magnified by the same amount would be over a mile (1. 6 kilometers) tall. Even with an ordinary microscope, you must look closely to see bacteria. Using a magnification of 100 times, one finds that bacteria are barely visible as tiny rods or dots. One cannot make out anything of their structure. Using special stains, one can see that some bacteria have attached to them wavy-looking " hairs" called flagella. Others have only one flagellum. The flagella rotate, pushing the bacteria through the water. Many bacteria lack flagella and cannot move about by their own power, while others can glide along over surfaces by some little-understood mechanism. From the bacterial point of view, the world is a very different place from what it is to humans. To a bacterium water is as thick as molasses is to us. Bacteria are so small that they are influenced by the movements of the chemical molecules around them. Bacteria under the microscope, even those with no flagella, often bounce about in the water. This is because they collide with the water molecules and are pushed this way and that. Molecules move so rapidly that within a tenth of a second the molecules around a bacterium have all been replaced by new ones; even bacteria without flagella are thus constantly exposed to a changing environment.

单选题A Tale of Scottish Rural Life Lewis Grassic Gibbon's Sunset Sony, (1932) was voted "the best Scottish novel of all time" by Scottish's reading public in 2005. Once considered shocking for its frank description of aspects of the lives of Scotland's poor rural farmers, it has been adapted for stage, film, TV and radio in recent decades. The novel is set on the fictional estate of Kinraddie, in the fanning country of the Scottish northwest in the years up to and beyond World War I. At its heart is the story of Chris, who is both part of the community and a little outside it. Grassic Gibbon gives us the most detailed and intimate account of the life of his heroine. We watch her grow through a childhood dominated by her cruel but hard-working father; experience tragedy (her mother's suicide and murder of her twin children); and learn about her feelings as she grows into woman. We see her marry, lose her husband, then marry again. Chris has seemed so convincing a figure to some female readers that they cannot believe that she is the creation of a man. But it would be misleading to suggest that this book is just about Chris. It is truly a novel of a place and its people. Its opening section tells of Kinraddie's long history, in a language that imitates the place's changing patterns of speech and writing. The story itself is amazingly full of characters and incidents. It is told from Chris' point of view but also from that of the gossiping community, a community where everybody knows everybody else's business and nothing is ever forgotten. Sunset Song has a social theme too. It is concerned with what Grassic Gibbon perceives as the destruction of traditional Scottish rural life first by modernization and then by World War I. Gibbon tried hard to show how certain characters resist the war. Despite this, the war takes the young men away, a number of them to their deaths. In particular, it takes away Chris' husband, Ewan Tavendale. The war finally kills Ewan, but not in the way his widow is told In fact, the Germans aren't responsible for his death, but his own side. He is shot because he is said to have run away from a battle. If the novel is about the end of one way of life it also looks ahead, it is a "Sunset Song" but is concerned too with the new Kinraddie, indeed of the new European world Grassic Gibbon went on to publish two other novels about the place that continue its story.

单选题It took us a long time to {{U}}mend{{/U}} the house

单选题William Wrigley sent free gum to every pretty woman in the US.

单选题Since 1939, numerous studies have been conducted to determine whether smoking is a health hazard. The trend of the evidence has been consistent and indicates that there is a serious health risk. Research teams have conducted studies that show beyond all reasonable doubt that tobacco smoking is associated with a shortened life expectancy. Cigarette smoking is believed by most research workers in this field to be an important factorin the development of caner of the lungs and cancer of the throat and is believed to be related to cancer of some other organs of the body. Male cigarette smokers have a higher death rate from bean disease than non--smoking males. Female smokers are thought to be less affected because they do not breathe in the smoke so deeply. Apart from statistics, it might be helpful to look at what smoking tobacco does to the human body. Smoke is a mixture of gases, vaporized chemicals, minute particles of ash and other solids. There is also nicotine, which is powerful poison, and black tar. As smoke is breathed in, all those components from deposits on the membranes of the lungs. One point of concentration is where the air tube and bronchus divides. Most lung cancer begins at this point. Filters and low tar tobacco are claimed to make smoking to some extent safer, but they can only slightly reduce, not eliminate the hazards. What is the main idea of the passage?A. Smoking is big hazard to health.B. There are ways to make smoking safe.C. Smoking is more hazardous to male smokers than to female smokers.D. There are many poisonous chemicals in tobacco.

单选题At the first explosion, the crowd {{U}}scattered{{/U}}. A. separated B. fled C. departed D. spread

单选题"Much of the sickness and death attributed to the major communicable diseases is in fact caused by malnutrition which makes the body less able to withstand infections when they strike," said Dr Hiroshi Nakajima, Director-General of the World Health Organization (WHO). "At the same time," he added, "in developing countries today, malnutrition is the cause of 174 million children under five years of age being (51) , and 230 million being stunted(阻碍)in their growth. Such (52) represent deprivation, suffering and wasted human potential (53) a scale that is unacceptable from every point of view. Whether we think in (54) of humanitarian concern, common justice or development needs, they demand a (55) , both from national governments and from the international community." It is now (56) that 6.6 million out of the estimated 12.2 million deaths (57) among children under-five--or 54% of young child mortality in developing countries-is associated with malnutrition, In some (58) , such as sub-Saha-ran Africa and south Asia, stagnation(停滞)of nutritional improvement (59) with a rapid rise in population has resulted in an (60) increase in the total number of malnourished children. (61) , over two-thirds of the world's malnourished children live in Asia (especially south Asia), followed by Africa and Latin America. As Dr Nakajima noted, "The globalization of industry, trade, travel and communication has brought (62) it unprecedented possibilities for mutual cooperation in (63) hunger and malnutrition. At the same time, however, the acceptability of certain foods, and the cultural aspects of their production, distribution and preparation, are now recognized as (64) in the promotion of good nutrition. Without the attention (65) them, little progress can be made towards household food security, appropriate diets, the control of micronutrient(微量元素)deficiencies, the promotion of breast-feeding, and other strategies listed in the Plan of Action adopted in 1992 (at the International Conference on Nutrition in Rome)./