单选题7. The union representative put across her argument very effectively.

单选题. Plants in Desert Only special plants can survive the terrible climate of a desert, for these are regions where the annual range of the soil temperature can be over 75℃. Furthermore, during the summer there are few clouds in the sky to protect plants from the sun's ray. Another problem is the fact that there are frequently strong winds that drive small, sharp particles of sand into the plants, tearing and damaging them. The most difficult problem for all forms of plant life, however, is the fact that the entire annual rainfall occurs during a few days or weeks in spring. Grasses and flowers in desert survive from one year to the next by existing through the long, hot, dry season in the form of seeds. These seeds remain inactive unless the right amount of rain falls. If no rain falls, or if insufficient rain falls, they wait until the next year, or even still the next. Another factor that helps these plants to survive is the fact that their life cycles are short. By the time the water from the spring rains disappears—just a few weeks after it falls—such plants no longer need any. The perennials (多年生植物) have special features that enable them to survive as plants for several years. Thus, nearly all desert perennials have extensive root systems below ground and a small shoot system above ground. The large root network enables the plant to absorb as much water as possible in short time. The small shoot system, on the other hand, considerably limits water loss by evaporation (蒸发). Another feature of many perennials is that after the rainy season they lose their leaves in preparation for the long, dry season, just as trees in wetter climates lose theirs in preparation for the winter. This reduces their water loss by evaporation during the dry season. Then, in next rainy season, they come fully alive once more, and grow new branches, leaves and flowers, just as the grasses and flowers in desert do.1. Grasses and flowers in desert are able to survive because they stay in the form of seeds to wait for the right amount of water to come.

单选题11. The great changes of the city astonished every visitor to that city.

单选题 Batteries Built by Viruses What do chicken pox

单选题5. These are their motives for doing it.

单选题8. The dentist has decided to extract her bad tooth.

单选题 In the situation comedy

单选题3. Have you talked to her lately?

单选题8. The police refused to disclose the clues they were working on.

单选题 As time went on

单选题 This is not typical of English

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.1. The 20 patients had stem cell injections instead of surgery.

单选题10. A large sum of money has been allocated for buying new books for the library.

单选题 At the age of 30

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 D-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 D-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.1. The results of the new study are unexpected.

单选题4. We've seen a marked shift in our approach to the social issues.

单选题10. She is a lovely and gracious woman.

单选题4. He often finds fault with my work.

单选题7. We were astonished to hear that their football team had won the champion.

单选题. Mother Nature Shows Her Strength Tornadoes (龙卷风) and heavy thunderstorms moved across the Great Lakes and into Trumbull County on Saturday evening: The storms were dramatic and dangerous. George Snyder was driving the fire truck down Route 88 when he first noticed that a funnel (漏斗状的) cloud was behind him. "I stopped the truck and watched the funnel cloud. It was about 100 feet off the ground and I saw it go up and down for a while. It was moving toward Bradley Road and then suddenly it disappeared," Snyder said. Snyder only saw one of the funnel clouds that passed through northeastern Ohio on Saturday. In Trumbull County, a tornado turned trees onto their sides. Some trees feel onto houses and cars. Other trees fell into telephone and electrical wires as they went down. Amanda Symcheck was having a party when the storm began. "I knew something was wrong," she said. "I saw the sky go green and pink (粉红色). Then it sounded like a train rushing toward the house. I started crying and told everyone to go to the basement for protection." The tornado caused a lot of damage to cars and houses in the area. It will take a long time and much money to repair everything. There was also serious water damage from the thunderstorms. The heavy rains and high wind caused the power to go out in many homes. The storms caused serious flooding in areas near the river. More than four inches of rain fell in parts of Trumbull County. The river was so hight that the water ran into streets and houses. Many streets had to be closed to cars and trucks because of the high water. This made it difficult for fire trucks, police cars, and other rescue vehicles to help people who were in trouble. Many people who live near the river had to leave their homes for their own safety. Some people reported five feet of water in their homes. Local and state officials opened emergency shelters for the people who were evacuated (撤走). The Red Cross served meals to them. "This was a really intense storm," said Snyder. "People were afraid. Mother Nature call be fierce. We were lucky this time. No one was killed."1. The weather was nice in Trumbull County on Saturday evening.