单选题The toy boat turned over and sank to the {{U}}bottom{{/U}} of the pool.

单选题{{B}}第二篇{{/B}} A new international study shows that six people die every minute from smoking. That equals 3 million deaths around the world every year. If the present rate (率)of smoking continues, the number of deaths each year from smoking could rise to 10 million by the year 2020. The study describes smoking as the biggest cause to deadly diseases among grown-ups in industrial countries. So far most of the smoking deaths have happened on men, especially in developing countries. A researcher at the World Health Organization says 70% of Chinese men smoke more than 15 cigarettes each day. In Latin America about 50% of the men are smokers. There also is a very large number of smokers in the former Soviet Union(苏联)and in the east Europe. And 25% of all smoking deaths worldwide are in those areas of the world. Scientists say smoking will kill 50% of the countries. Smoking is known to cause lung cancer. It also can lead to cancer of the mouth and other parts of bodies. Smokers are more likely than non-smokers to suffer from heart disease. Experts say that people reduce their chance of dying from smoking if they stop smoking completely. They say smokers who give up smoking can improve their health.

单选题Fine freshwater pearls are found in the main stream and the tributaries of the Mississippi River.A. banksB. deltasC. branchesD. currents

单选题The most {{U}}pressing{{/U}} problem any economic system faces is how to use its scarce resources. A.puzzling B.difficult C.terrifying D.urgent

单选题The Klondike was the Uscene/U of one of the biggest gold rashes the world has ever known.

单选题Although Peter is only 25 years old, he earns a large income.A. respectfulB. respectableC. respectiveD. respected

单选题Loud noises can be {{U}}annoying{{/U}}.

单选题In a bullfight, it is the movement, not the color, of objects that arouses the bull.

单选题She shows little Uregard/U for the feelings of others and does exactly what she wants to.

单选题A Sunshade for the Planet Even with the best will in the world, reducing our carbon emissions is not going to prevent global wanning. It has become clear that even if we take the strongest measures to control emissions, the uncertainties in our climate models still leave open the possibility of extreme warming and rises in sea level. At the same time, resistance by governments and special interest groups makes it quite possible that the actions suggested by climate scientists might not be implemented soon enough. Fortunately, if the worst comes to the worst, scientists still have a few tricks up their sleeves. For the most part they have strongly resisted discussing these options for fear of inviting a sense of complacency that might thwart efforts to tackle the root of the problem. Until now, that is, a growing number of researchers are taking a fresh look at large-scale "geo-engineering" projects that might be used to counteract global wanning. "I use the analogy of methadone," says Stephen Schneider, a climate researcher at Stanford University in California who was among the first to draw attention to global warming. "If you have a heroin addict, the correct treatment is hospitalization and a long rehab. But if they absolutely refuse, methadone is better than heroin. " Basically the idea is to apply "sunscreen" to the whole planet. One astronomer has come up with a radical plan to cool Earth; launch trillions of feather-light discs into space, where they would form a vast cloud that would block the sun's rays. It's controversial, but recent studies suggest there are ways to deflect just enough of the sunlight reaching the Earth's surface to counteract the warming produced by the greenhouse effect. Global climate models show that blocking just 1.8 per cent of the incident energy in the sun's rays would cancel out the warming effects produced by a doubling of greenhouse gases in the atmosphere. That could be crucial, because even the most severe emissions-control measures being proposed would leave us with a doubling of carbon dioxide by the end of this century, and that would last for at least a century more.

单选题You should {{U}}cultivate{{/U}} the habit of reading carefully.

单选题Lifetime employment influences one's

单选题These gases pollute the Uatmosphere/U of towns and cities.

单选题Below 600 feet ocean waters range from {{U}}dimly{{/U}} lit to completely dark. A. inadequately B. hardly C. faintly D. sufficiently

单选题Thousands of people perished in the storm. A. died B. suffered C. floated D. scattered

单选题Spacing in Animals Flight Distance Any observant person has noticed that a wild animal will allow a man or other potential enemy to approach only up to a given distance before it flees. "Flight distance" is the term used for this interspecies spacing. As a general rule, there is a positive relationship between the size of an animal and its flight distance — the larger the animal, the greater the distance it must keep between itself and the enemy. An antelope will flee when the enemy is as much as five hundred yards away. The wall lizard's flight distance, on the other hand is about six feet. Flight is the basic means of survival for mobile creatures. Critical Distance Critical distance apparently is present wherever and whenever there is a flight reaction. "Critical distance" includes the narrow zone separating flight distance from attack distance. A lion in a zoo will flee from an approaching man until it meets a barrier that it cannot overcome. If the man continues the approach, he soon penetrates the lion's critical distance, at which point the cornered lion reverses direction and begins slowly to stalk the man. Social Distance Social animals need to stay in touch with each other. Loss of contact with the group can be fatal for a variety of reasons including exposure to enemies. Social distance is not simply the distance at which an animal will lose contact with his group — that is, the distance at which it can no longer see, hear, or smell the group - it is rather a psychological distance, one at which the animal apparently begins to feel anxious when he exceeds its limits. We can think of it as a hidden band that contains the group. Social distance varies from species to species. It is quite short — apparently only a few yards — among some animals, and quite long among others. Social distance is not always rigidly fixed but is determined in part by the situation. When the young of apes and humans are mobile but not yet under control of the mother's voice, social distance may be the length of her reach. This is readily observed among the baboons in a zoo. When the baby approaches a certain point, the mother reaches out to seize the end of its tail and pull it back to her. When added control is needed because of danger, social distance shrinks. To show this in man, one has only to watch a family with a number of small children holding hands as they cross a busy street.

单选题Stem Cell Therapy May Help Repair the Heart According to scientists in the USA, stem cell therapy may one day be able to repair the hearts of people with heart failure. Researchers at Pittsburgh University School of Medicine examined 20 patients who had severe heart failure and were going to have surgery. They injected stem cells into the parts of their hearts that were damaged. They then compared their hearts with those of people who had undergone surgery without having the stem cells injected into them (they had also suffered from severe heart failure). The patients who had the stem cells injected had hearts that were able to pump (用泵抽水) more blood than the others. According to Professor Robert Kormos, one of the researchers, these results could revolutionize heart treatment. Although previous studies had indicated that there might be a benefit, this is the first study that has actually proved that stem cell therapy can help the failing heart work better. All the patients in this study had hearts that could not pump blood properly. The scientists measured their ejection fraction (射血分数). This is a measure of heart performance; you measure how much blood is being pumped out by the left ventricle (心室). Healthy people"s ejection fraction is about 55%. These patients had ejection fraction of under 35%. They all had by-pass surgery (搭桥手术) performed on them. Some of the patients had stem cells taken from their hip bones and injected into 25-30 sites in the damaged heart muscle. Six months later their ejection fraction rate was 46.1% while those who just had surgery but no stem cell injections averaged 37.2%. No side effects were reported. Heart failure is a common problem all over the world. In the UK alone about 650,000 people suffer from heart failure every year. As the number of people suffering from heart failure increases in the world in general these findings are particularly significant. Current treatments relieve the symptoms. This new stem cell therapy actually repairs the damaged muscle in the heart and has the potential of curing the disease.

单选题We had to {{U}}abandon{{/U}} the car and walk the rest of the way.

单选题The food is insufficient for three people.A. instantB. infiniteC. inexpensiveD. inadequate

单选题It is virtually impossible to persuade him to apply for the job.