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.

单选题The president {{U}}proposed{{/U}} that we should bring the meeting to a close. A. stated B. said C. suggested D. announced

单选题You possess {{U}}affluence{{/U}}, but it doesn't mean you can have everything in hand.

单选题He failed the exam again because he was so careless.A. uselessB. attentionlessC. foolishD. handsome

单选题According to Campbell, health education should be centred on

单选题15 I expect that she will be able to cater for your particular needs.

单选题The AIDS Uconvention/U will be held in Glasgow.

单选题Canada will prohibit smoking in all offices later this year.

单选题A limited number of books on this subject are in the library.

单选题Hearingproblems may be alleviated by changes in diet and exercisehabits.

单选题 阅读下面的短文，文中有15处空白，每处空白给出了4个选项，请根据短文的内容从4个选项中选择1个最佳答案。 {{B}} Passive Smoking is Workplace Killer{{/B}} Pressure mounted on Britain on Monday to take action on{{U}} (1) {{/U}}smoking with new research showing second-hand smoke{{U}} (2) {{/U}}about one worker each week in the hospitality industry. Professor Konrad Jamrozik, of Imperial College in London, told a conference on environmental tobacco that second-hand{{U}} (3) {{/U}}kills 49 employees in pubs, bars, restaurants and hotels each year and contributes to 700 deaths from lung cancer, heart{{U}} (4) {{/U}}and stroke across the total national work force. "Exposure in the hospitality{{U}} (5) {{/U}}at work outweighs the consequences of exposure of living.{{U}} (6) {{/U}}a smoker for those staff. "Jamrozik said in an interview. Other{{U}} (7) {{/U}}have measured the levels of exposure to passive smoking but Jamrozik calculated how it would translate into avoidable deaths. His findings are{{U}} (8) {{/U}}on the number of people working in the hospitality industry in Britain, Their exposure to second hand smoke and their{{U}} (9) {{/U}}of dying from it. Jamrozik said me findings would apply to{{U}} (10) {{/U}}countries in Europe because, to a greater or{{U}} (11) {{/U}}extent, levels of smoking in the community are similar. Professor Carol Black, president of the Royal College of Physicians, who sponsored the meeting said the research is proof of the need for a ban on smoking in{{U}} (12) {{/U}}places. "Environmental tobacco smoke in pubs, bars, restaurants and other public places is{{U}} (13) {{/U}}damaging to the health of employees as well as the general public," she said in a statement. "Making these places smoke-free not only protects vulnerable staff and the public. It will{{U}} (14) {{/U}}help over 300, 000 people in Britain to stop smoking completely," she added. Ireland recently became the first country to introduce a national ban on smoking in Public{{U}} (15) {{/U}}. New York and parts of Australia have taken similar measures. workplace n. 工作场所:车间 hospitality n. 友好款待;好客;殷勤 imperial adj. 英联邦的 outweigh vt. 在重要性(或价值上)超过 vulnerable adj. 易受伤的;脆弱的

单选题Listening to Birdsong A male zebra finch chirps away to himself. Suddenly he notices a female bird nearby. He realizes he has an audience and immediately changes his song. Can the female tell the difference in his performance? According to a new study, the female zebra finch knows. And she prefers the special trills he creates when he sings to her. A male zebra finch changes his song when singing to a female in ways that people can barely detect. But the female finch can tell the difference. Scientists had noticed slight variations in the songs of male zebra finches based on whether they were singing alone or whether there was a female (and potential mate) nearby. With an audience, the males sped up the pace of their songs and controlled the notes they used. For this study, researchers Sarah C. Woolley and Allison Doupe at the University of California, San Francisco decided to focus attention on the listening females, which have not been well studied in the past. In the study, Woolley and Doupe set up, a long cage with a sound speaker at each end. One broadcast the sound of a male zebra finch singing to himself, like someone singing in the shower. The other speaker broadcast a male performing for a female audience, as if he was giving a concert. Female birds were placed between the two speakers. Some of the birds had mates. Others didn"t. The females shifted around a bit, and then most of them hopped over to sit beside just one speaker. All the birds that made a clear choice liked songs meant for a female audience, even if they"d never met the male. Mated females also had a chance to listen to two different performance songs, one from an unknown male, and one from their mate. They spent more time listening to the concert version of their mates" songs. This suggests that after a while, females learn to recognize—and prefer—the songs of their mates. Scientists then studied the brains of the females. They found certain areas of the brain perked up when the birds listened to the concert songs. These brain areas may be involved in recognizing and evaluating the songs, and storing the memories of them. This research deals with what"s called directed communication, when the communicator, or sender, focuses the message for a specific audience. One example is the way moms speak to their babies. Mothers around the world use the same sort of high-pitched sing-song chatter, and the babies respond best to those sounds. Songbirds are one of the only other species known to learn their communication, in this case their songs.