单选题 After a long delay, she ______ replying to my e-mail.

单选题The old woman is {{U}}chronically{{/U}} ill in bed and seldom goes out.

单选题 Questions16-19 are based on the recording you have just heard.

单选题At the conference he expressed some personal views which brought him into ( ) with the Party leadership.

单选题Compared with the new teachers, ______.

单选题Gene therapy and gene-based drugs are two ways we could benefit from our growing mastery of genetic science. But there will be others as well. Here is one of the remarkable therapies on the cutting edge of genetic research that could make their way into mainstream medicine in the coming years. While it's true that just about every cell in the body has the instructions to make a complete human, most of those instructions are inactivated, and with good reason: the last thing you want for your brain cells is to start churning out stomach acid or your nose to turn into a kidney. The only time cells truly have the potential to turn into any and all body parts is very early in a pregnancy, when so-called stem cells haven't begun to specialize. Yet this untapped potential could be a terrific boon to medicine. Most diseases involve the death of healthy cells--brain cells in Alzheimer's, cardiac cells in heart disease, pancreatic cells in diabetes, to name a few. If doctors could isolate stem cells, then direct their growth, they might be able to furnish patients with healthy replacement tissue. It was incredibly difficult, but last fall scientists at the University of Wisconsin managed to isolate stem cells and get them to grow into neural, gut, muscle and bone cells. The process still can't be controlled, and may have unforeseen limitations. But if efforts to understand and master stem-cell development prove successful, doctors will have a therapeutic tool of incredible power. The same applies to cloning, which is really just the other side of the coin; true cloning, as first shown with the sheep Dolly two years ago, involves taking a developed cell and reactivating the genome within, resetting its developmental instructions to a pristine state. Once that happens, the rejuvenated cell can develop into a full-fledged animal, genetically identical to its parent. For agriculture, in which purely physical characteristics like milk production in a cow or low fat in a hog have real market value, biological carbon copies could become routine within a few years. This past year scientists have done for mice and cows what Ian Wilmot did for Dolly, and other creatures are bound to join the cloned menagerie in the coming year. Human cloning, on the other hand, may be technically feasible but legally and emotionally more difficult. Still, one day it will happen. The ability to reset body cells to a pristine, undeveloped state could give doctors exactly the same advantages they would get from stem cells: the potential to make healthy body tissues of all sorts, and thus to cure disease. That could prove to be a true "miracle cure./

单选题______telling her again since she won't listen to it?

单选题How can he do so much work? He ______ stay late at the office every evening and take work home at weekends. A. must B. might C. can't D. would

单选题 中国城市急剧膨胀，大量农村人口移居城镇，使城市变得拥挤不堪。城市人口的迅速增长，将对公共卫生、淡水供应、医疗保健、食品供应、住房、交通和就业造成极大压力，并且带来一些恶性(Vicious)社会问题。同时，由于城镇发展，我们失去了肥沃的农田(fertile farmland)，日益恶化的空气质量和水质的污染使农作物受到损害。所有这些将使农业发展更加步履维艰。地球资源日益匮乏也是一个不容忽视的问题。看来解决人口激增的问题，是摆在现代人面前的一项艰巨而迫切的(pressing)任务。

单选题Can animals have a sense of humor? Sally Blanchard, publisher of a newsletter called the Pet Bird Report, thinks a pet parrot may have pulled her leg. That's one explanation for the time her African gray parrot, named Bongo Marie, seemed to feign distress at the possible death of an Amazon parrot named Paco. It happened one day when Blanchard was making Cornish game hen for dinner. As Blanchard lifted her knife, the African gray threw back its head and said, "Oh, no! Paco!" Trying not to laugh, Blanchard said, "That's not Paco," and showed Bongo Marie that the Amazon was alive and well. Mimicking a disappointed tone, Bongo Marie said, "Oh, no," and launched into a hoarse laugh. Was the parrot joking when it seemed to believe the other bird was a goner? Did Bongo Marie comprehend Blanchard's response? Studies of African grays have shown that they can understand the meaning of words--for example, that red refers to a color, not just a particular red object. Parrots also enjoy getting a reaction out of humans, and so, whether or not Bongo Marie's crocodile tears were intentional, the episode was thoroughly satisfying from the parrot's point of view.

单选题What feature sets apart the three dictionaries discussed in the passage from traditional ones ?

单选题______I ve seen how he lives, I know why he needs so much money.

单选题Which of the following is NOT mentioned in the passage as a function of electronics in television transmissions?

单选题The Great Wall is a great tourist ______ , drawing millions of visitors from all parts of the world every year.

单选题Children would play with fire until their hands were burnt away if______.

单选题Coconut椰子is an unusual food for many reasons.It is one of the largest edible seeds produced by any plant.Its unusual contents also make it unique in the seed world—it consists of both “meat“ and “wate

单选题 ________ how to solve the mathematics problem, Stephanie asked her teacher for help.