Although we already know a great deal about influenza, and although the World Health Organization is constantly collecting detailed information from its chain of influenza reference laboratories throughout the world, it is extremely difficult for epidemiologists (流行病专家), who study infectious disease, to predict when and where the next flu epidemic will occur, and how severe it will be.
There are three kinds of influenza virus, known as A, B and C. Influenza C virus is relatively stable and causes mild infections that do not spread far through the population. The A and B types are unstable, and are responsible for the epidemics that cause frequent concern. Following any virus attack, the human body builds up antibodies which confer immunity to that strain of virus, but a virus with the capacity to change its character is able to by-pass this protection. Variability is less developed in the influenza B virus, which affects only human beings. An influenza B virus may cause a widespread epidemic but will have little effect if introduced into the same community soon afterwards, since nearly everyone will have built up antibodies and will be immune. The influenza A virus, which affects animals also, is extremely unstable and is responsible for some of the worst outbreaks of the disease, such as the unparalleled pandemic, or world epidemic, of 1918-1919, when about half the world’s population were infected and about twenty million people died, some from pneumonia caused by the virus itself and some from secondary complications(并发症) caused by bacteria.
Accurate prediction is difficult because of the complication of the factors. A particular virus may be related to one to which some of the population have partial involved immunity. The extent to which it will spread will depend on factors such as its own strength, or virulence, the ease with which it can be transmitted and the strength of the opposition it encounters. Scientists, however, have a reliable general picture of the world situation. Influenza A attacks us in waves every two or three years, while influenza B, which travels more slowly, launches its main assaults every three to six years. The outbreaks vary from isolated cases to epidemics involving a tenth or more of the population. We may confidently prophesy that sooner or later large numbers of people will be feeling the unpleasant effects of some kind of influenza virus.

What does the author say about the influenza B virus（）

A:B virus is relatively stable and causes mild infections that do not spread far through the population B:B virus is unstable, and is responsible for the epidemics that cause frequent concern C:B virus is extremely unstable and is responsible for some of the worst outbreaks of the disease D:B virus has a very developed variability, and it affects only human beings.

C The behavior of a building’s users may be at least as important as its design when it comes to energy use, according to new research from the UK Energy Research Centre (UKERC). The UK promises to reduce its carbon emissions (排放）by 80 percent by 2050, part of which will be achieved by all new homes being zero-carbon by 2016. But this report shows that sustainable building design on its own — though extremely important- is not enough to achieve such reductions: the behaviour of the people using the building has to change too. The study suggests that the ways that people use and live in their homes have been largely ignored by existing efforts to improve energy efficiency (效率)，which instead focus on architectural and technological developments. ‘Technology is going to assist but it is not going to do everything,’explains Katy Janda, a UKERC senior researcher，‘consumption patterns of building users can defeat the most careful design. ’In other words，old habits die hard, even in the best-designed eco-home. Another part of the problem is information. Households and bill-payers don’t have the knowledge they need to change their energy-use habits. Without specific information，it’s hard to estimate the costs and benefits of making different choices. Feedback (反馈） facilities, like smart meters and energy monitors，could help bridge this information gap by helping people see how changing their behaviour directly affects their energy use; some studies have shown that households can achieve up to 15 percent energy savings using smart meters. Social science research has added a further dimension (方面），suggesting that individuals’behaviour in the home can be personal and cannot be predicted 一 whether people throw open their windows rather than turn down the thermostat (恒温器) , for example. Janda argues that education is the key. She calls for a focused programme to teach people about buildings and their own behaviour in them. The information gap in energy use _______.

A:can be bridged by feedback facilities B:affects the study on energy monitors C:brings about problems for smart meters D:will be caused by building users’ old habits

Marriage in Men’s Lives is a courageous and innovative book: courageous because it tackles a politically and socially charged issue—marriage as a social institution—in a time when texts on the family portray marriage as just one of any number of equally valuable lifestyle choices; innovative because it looks closely at the ways in which a key social institution affects individuals, in this case, the way that marriage affects men.
Even as sex differences within marriage have diminished, the role of husband still plays a unique function in the lives of men. Steven Nock argues that adolescent boys face challenges in becoming men that adolescent girls do not face in becoming women. According to Nock, "Masculinity is precarious and must be sustained in adulthood. Normative marriage does this. A man develops, sustains, and displays his masculine identity in his marriage. The adult roles that men occupy as husbands are core aspect of their masculinity." The behaviors expected of married men as husbands, according to Nock, are the same behaviors expected of husbands as men. So getting married and successfully doing the things that husbands do allows men to achieve and sustain their masculinity.
Nock argues that if marriage provides a mechanism through Which men establish and maintain their masculinity, marriage should have consistent and predictable consequences. He reasons that normative marriage will have different consequences than other forms of marriage. Nock argues that marriage causes men to become more successful, participate in social life, and to become more philanthropic. This is, in today’s climate of extreme caution about causal relationships, a bold claim. He tests it using data from the National Longitudinal Survey of Youth and fixed effect models, to separate changes that accompany aging from those that happen uniquely at marriage. To measure achievement, Nock uses annual income, annual weeks worked, and occupational prestige. He measures social participation with time spent on housework, social contacts, and organizational involvement; and he measures generosity with gifts to non-relatives and loans to relatives and non-relatives.
To summarize his results too briefly, when men marry, their achievements rise on all measures; they reduce their time in housework; increase their contact with relatives, church services and church events, and coworkers; and decrease contact with friends and time in bars. When men marry, they give fewer and smaller gifts and loans to non-relatives and more and larger loans to relatives. Nock also looks at changes in each of the measures of adult achievement, social participation, and generosity with changes in each of the dimensions of normative marriage. He finds, generally, that moves toward normative marriage increase achievements, social participation with family and religious organizations, and generosity to relatives. Changes toward more normative marriage also reduce men’s time in housework, their social contacts with friends, and social events in bars.
It can be inferred from the first paragraph that

A:Nock is a strong advocate for keeping the marriage tradition. B:nowadays most people choose not to marry. C:the way that marriage affects men is more important than the way it affects women. D:Nock considers marriage only as one of the many equally valuable lifestyle choices.

One of the most pressing challenges that the United States—and indeed, the world—will face in the next few decades is how to alleviate the growing stress that human activities are placing on the environment. The consequences are just too great to ignore. Wildlife habitats are being degraded or disappearing altogether as new developments take up more land. Plant and animal species are becoming extinct at a greater rate now than at any time in Earth’s history. As many as 30 percent of the world’s fish stocks are overexploited. And the list goes on.
Yet, there is reason to have hope for the future. Advances in computing power and molecular biology are among the tremendous increases in scientific capability that are helping researchers gain a better understanding of these problems. Recent developments in science and technology could provide the basis for some major, and timely actions that would improve our understanding of how human activities affect the environment.
One priority for research is improving hydrological forecasting. It has been estimated that the world’s water use could triple in the next two decades. Already, widespread water shortages have occurred in parts of China, India, North Africa, and the Arabian Peninsula. The need for water also is taking its toll on freshwater ecosystems in the United States. Only 2 percent of the nation’s streams are considered in good condition, and close to 40 percent of native fish species are rare to extinct. Using a variety of new remote sensing tools, scientists can learn more about how precipitation affects water levels, how surface water is generated and transported, and how changes in the landscape affect water supplies.
To prevent outbreaks of infectious diseases in plants, animals, and humans, more study is needed on how pathogens, parasites, and disease-carrying species—as well as humans and other species they infect— are affected by changes in the environment. The overuse of antibiotics both in humans and in farm animals has contributed to the growth of antibiotic-resistant microorganisms. Researchers can take advantage of new technologies in genetics and computing to better monitor and predict the effects that environmental changes might have on disease outbreaks.
Humans have made alterations to Earth’s surface—such as tropical deforestation, reduction of surface and ground water, and massive development—so dramatic that they approach the levels of transformation that occurred during glacial periods. Such alterations cause changes in local and regional climate, and will determine the future of agriculture. Recent advances in data collection and analysis should be used to document and better understand the causes and consequences of changes in land cover and use.
Which of the following does the author NOT suggest as an important area for research

A:How precipitation affects water levels. B:How to prevent outbreaks of infectious diseases. C:How urban development affects the environment. D:How the industrial pollution impacts the environment.

On Sunday, April 22, 1990, people all over the world celebrated the same holiday. It was the twentieth anniversary of Earth Day. The purpose of the holiday, which we celebrate every year on that date, is to help people learn how to protect the planet Earth. People around the world celebrate Earth Day because they worry about the planet. Many forms of animal life are disappearing from the earth. Carelessness and accidents in many countries have caused problems that are harmful to the environment. Air and water pollution, oil spills, and toxic waste are some of the serious problems.
In fact, protecting the earth is truly a worldwide issue. Pollution in one place often affects areas far away. For example, an accident in a nuclear power plant in one country can create a radioactive cloud that goes halfway around the world. Factory smoke in one country can cause acid rain in another. It is easy to see how our protecting the environment has become an international issue.
So, in order to begin the difficult job of saving the earth, people around the world did special things on Earth Day, 1990. In Japan, divers pulled garbage from the sea. In Nepal, hikers picked up trash on Mount Everest. Students marched in support of Earth Day in Hong Kong, and people planted medicinal herbs in the Philippines. In the United States, children planted trees. Native Americans told legends about the creation of the earth, artists drew pictures on walls next to highways, and musicians gave concerts to Support the work of environmental groups. Almost everyone everywhere stopped for a moment to think about how we can protect the earth.

Protecting the earth is a worldwide question because （）

A:pollution is everywhere in the world B:polluted air and water in one place affects distant areas C:people all over the world are responsible for the pollution problem D:all of the above

On Sunday, April 22, 1990, people all over the world celebrated the same holiday. It was the twentieth anniversary of Earth Day. The purpose of the holiday, which we celebrate every year on that date, is to help people learn how to protect the planet Earth. People around the world celebrate Earth Day because they worry about the planet. Many forms of animal life are disappearing from the earth. Carelessness and accidents in many countries have caused problems that are harmful to the environment. Air and water pollution, oil spills, and toxic waste are some of the serious problems.
In fact, protecting the earth is truly a worldwide issue. Pollution in one place often affects areas far away. For example, an accident in a nuclear power plant in one country can create a radioactive cloud that goes halfway around the world. Factory smoke in one country can cause acid rain in another. It is easy to see how our protecting the environment has become an international issue.
So, in order to begin the difficult job of saving the earth, people around the world did special things on Earth Day, 1990. In Japan, divers pulled garbage from the sea. In Nepal, hikers picked up trash on Mount Everest. Students marched in support of Earth Day in Hong Kong, and people planted medicinal herbs in the Philippines. In the United States, children planted trees. Native Americans told legends about the creation of the earth, artists drew pictures on walls next to highways, and musicians gave concerts to Support the work of environmental groups. Almost everyone everywhere stopped for a moment to think about how we can protect the earth.

Protecting the earth is a worldwide question because （）

A:pollution is everywhere in the world B:polluted air and water in one place affects distant areas C:people all over the world are responsible for the pollution problem D:all of the above

Scientists who study insects have a real mystery on their hands. All across the country, honeybees are leaving their hives and never returning. Researchers call this phenomenon colony-collapse disorder. According to surveys of beekeepers across the country, 25 to 40 percent of the honeybees in the United States have vanished from their hives since last fall. So far, no one can explain why.
Colony collapse is a serious concern because bees play an important role in the production of about one-third of the foods we eat. As they feed, honeybees spread pollen from flower to flower. Without this process, a plant can’t produce seeds or fruits.
Now, a group of scientists and beekeepers have teamed up to try to figure out what’s causing the alarming collapse of so many colonies. By sharing their expertise in honeybee behavior, health, and nutrition, team members hope to find out what’s contributing to the decline and to prevent bee disappearances in the future.
It could be that disease is causing the disappearance of the bees. To explore that possibility, Jay Evans, a researcher at the United States Department of Agriculture (USDA Bee Research Laboratory, examines bees taken from colonies that are collapsing. "We know what s healthy bee should look like on the inside, and we can look for physical signs of disease," he says. And bees from collapsing colonies don’t look very healthy. "Their stomachs are worn down, compared to the stomachs of healthy bees," Evans says. It may be that a parasite is damaging the bees’ digestive organs. Their immune systems may not be working as they should. Moreover, they have high levels of bacteria inside their bodies.
Another cause of colony-collapse disorder may be certain chemicals that farmers apply to kill unwanted insects on crops, says Jerry Hayes, chief bee inspector for the Florida Department of Agriculture. Some studies, he says, suggest that a certain type of insecticide affects the honeybee’s nervous system (which includes the brain) and memory. "It seems like honeybees are going out and getting confused about where to go and what to do," he says.
If it turns out that a disease is contributing to colony collapse, bees’ genes could explain why some colonies have collapsed and others have not. In any group of bees there are many different kinds of genes. The more different genes a group has, the higher the group’s genetic diversity. So far scientists haven’t determined the role of genetic diversity in colony collapse, but it’s a promising theory, says Evans.
What explanation is given by Jerry Hayes to the phenomenon

A:Farmers apply certain chemicals to kill unwanted bees. B:The insecticide destroys the honeybee’s nervous system. C:The insecticide affects the honeybee’s memory. D:All of the abov