单选题To say that his resignation was a shock would be an______-------it caused panie.

单选题Her dietician suggested that _____diet and moderate exercise would help her recover soon.

单选题Salt, and not oil, is______ in water.

单选题In fear for their lives and in______ of their freedom, thousands of enslaved women and children fled to the Northern States on the eve of the American Civil War.(2007年中国科学院考博试题)

单选题American people ignore cultural differences in other countries because ______.

单选题Scientists generally hold that language has been so long in use that the length of time writing is known to cover is ______in Comparison. A.overwhelming B.uninspiring C.astounding D.trifling

单选题 About twice every century, one of the massive stars in our galaxy blows itself apart in a supernova explosion that sends massive quantities of radiation and matter into space and generates shock waves that sweep through the arms (a narrow extension of a larger area, mass, or group) of the galaxy. The shock waves heat the interstellar gas, evaporate small clouds, and compress larger ones to the point at which they collapse under their own gravity to form new stars. The general picture that has been developed for the supernova explosion and its aftermath goes something like this. Throughout its evolution, a star is much like a leaky balloon. It keeps its equilibrium figure through a balance of internal pressure against the tendency to collapse under its own weight. The pressure is generated by nuclear reactions in the core of the star which must continually supply energy to balance the energy that leaks out in the form of radiation. Eventually the nuclear fuel is exhausted, and the pressure drops in the core. With nothing to hold it up, the matter in the center of the star collapses inward, creating higher and higher densities and temperatures, until the nuclei and electrons are fused into a super-dense lump of matter known as a neutron star. As the overlying layers rain down on the surface of the neutron star, the temperature rises, until with a blinding flash of radiation, the collapse is reversed. A thermonuclear shock wave runs through the now expanding stellar envelope, fusing lighter elements into heavier ones and producing a brilliant visual outburst that can be as intense as the light of 10 billion suns. The shell of matter thrown off by the explosion plows through the surrounding gas, producing an expanding bubble of hot gas, with gas temperatures in the millions of degrees. This gas will emit most of its energy at X-ray wavelengths, so it is not surprising that X-ray observatories have provided some of the most useful insights into the nature of the supernova phenomenon. More than twenty supernova remnants have now been detected in X-ray studies. Recent discoveries of meteorites with anomalous concentrations of certain isotopes indicate that a supernova might have precipitated the' birth of our solar system more than four and a half billion years ago, Although the cloud that collapsed to form the sun and the planets was composed primarily of hydrogen and helium, it also contained carbon, nitrogen, and oxygen, elements essential for life as we know it. Elements heavier than helium are manufactured deep in the interior of stars and would, for the most part, remain there if it were not for the cataclysmic supernova explosions that blow giant stars apart. Additionally, supernovas produce clouds of high- energy particles called cosmic rays. These high-energy particles continually bombard the earth and are responsible for many of the genetic mutations that are the driving force of the evolution of species.

单选题The letter said that there was an______, but I couldn' t find where it was.

单选题More and more people nowadays are exercising, {{U}}quitting{{/U}} tobacco, losing weight and becoming more health-conscious.

单选题Scarcely does anyone want to become janitors, but to be appointed as a {{U}}sanitary{{/U}} engineer is quite something else.

单选题"Smart Symptom Wizard" is capable of ______.

单选题As a professional doctor, I will prescribe ______ for the good of my patients according to my ability and my judgment and never do harm to anyone. A. regimen B. equity C. requisite D. regime

单选题"It was the beginning of a revolution in America and the world, a revolution that some have yet to acknowledge and many have yet to appreciate," says Harold Skramstad, president of the Henry Ford Museum in Dearborn, Michigan. 1776? No indeed: 1896, when Frank Duryea finally perfected the Duryea Motor, Wagon. At its first airing, the contraption rolled less than 100 metres before the transmission froze up. But by the end of 1896 Duryea had sold 13 of them, thus giving birth to the American motor industry. That industry (whose roots, outside America, are usually attributed to tinkerings by Messrs Daimler and Benz in Germany) is being celebrated hugely over the coming months, culminating with a Great American Crnise-in in Detroit in June. "Our goal is to attract the greatest collection of antique and classic cars this nation has ever seen in one place at one time," says Mr Skramstad modestly. Americans may indeed blame the car for almost everything that has happened to their country, and themselves, since 1896. The car has determined. The way they live. From cradle to grave, the car marks every rite of American passage. Home by car from the maternity ward; first driving licence (usually at the age of 16); first (backseat) sexual experience; first car of one's own (and the make of car is a prime determinant of social status, symbolic of everything a person is or does). In Las Vegas, and elsewhere, Americans can get married at drive-in chapels. They then buy, or lust after, a house with garages big enough for not one but two or three cars. This allocates more space to cars than to children. And when the time comes, they may lie in state at a drive-through funeral home, where you can pay your respects without pulling over. The way they shop. Main Street has been replaced by the strip mall and the shopping mall, concentrating consumer goods in an auto-friendly space. A large part of each shopping trip must now be spent, bags under chin, searching for the place where the car was left. (And another point: bags have annoyingly lost their carrying handles since shoppers ceased to be pedestrian) Since car-friendly living and shopping became the role, most built-up parts of America now look like every other part. There is simply no difference between a Burger Inn in California and one on the outskirts of Boston. The way they eat. A significant proportion of Americans' weekly meals are now consumed inside cars, sometimes while parked outside the (drive-by) eatery concerned, sometimes en route, which leads to painful spillages in laps, leading to overburdening of. The legal system. Dozens of laws have been written to deal with car cases, ranging from traffic disputes to product liability. Drive-by shootings require a car, as do most getaways. The car is a great crime accessory; and it also causes the deaths of nearly 40,000 Americans every year. Personal finances. Before the age of the car, few people went into debt; no need to borrow money to buy a horse. Now Americans tie themselves up with extended installment loans, and this in turn has spawned a whole financial industry. The wealth of the nation. By 1908, an estimated 485 different manufacturers were building cars in the United States. Employment grew nearly 100-fold in the industry during the first decade of the 20th century. When Henry Ford, in a stroke of genius, automated his production line he required a rush of new, unskilled labour, which he enticed by offering an unheard-of ＄5 a day in wages. Henceforth, workers could actually afford to buy what they built. And Americans never looked back. Today, the Big Three car manufacturers (Food, GM and Chrysler) generate more than ＄200 billion a year in business inside the United States. Directly and indirectly, the industry employs roughly one in seven workers. Every car job is reckoned to add ＄100,000 in goods and services to the economy, twice the national average. People occasionally suppose that the car is under attack as it enters its second century. Environmental regulators and transport planners (with their talk of car pools and subways) tend to give this impression. There are signs that personal computers may be replacing the sports car as the chief passion, and expense, of young men. But, in the end, nothing beats the idea of individual mobility. In a society that values freedom above all, the obvious way to celebrate a centenary is just to keep driving.

单选题According to the passage, the original proponents of the Fourteenth Amendment were primarily concerned with ______.

单选题Almost overnight, Ames became a hero of environmentalists when his finding led to new and ______ bans on certain chemicals. A. regulations B. authorities C. orders D. suggestions

单选题An ethics crisis at one of the world's most successful human embryonic stem cell laboratories has plunged the controversial field of research into a new swirl of uncertainty. The accusations surrounding Korean cloning expert Woo Suk Hwang of Seoul National University--the first scientist to grow stem cells inside cloned human embryos--has already killed a spate of planned studies that sought to prove the cells' medical potential. The claims that Hwang may have obtained human eggs for his studies from women who felt pressured to donate are also reigniting a long-smoldering debate in the United States over the ethics of paying young women for their eggs, which are difficult to obtain but essential to the production of stem cells tailored to individuals. Egg donation, which is generally safe but occasionally leads to serious and even life-threatening complications, has been a wedge issue in the stem cell debates, linking feminists and other liberal thinkers to conservatives who favor tighter limits on stem cell research. "We're in danger of making women into guinea pigs for this research even before there are any treatments to be tested," said Marcy Darnovsky, associate director of the Center for Genetics and Society in Oakland, Calif. "We really need clear rules that someone is enforcing." With current techniques, it takes dozens of eggs to make a single cloned human embryo, which is destroyed in the process of extracting the stem cells. That means that if the field of therapeutic cloning is to advance--a field involving the creation of cloned embryos as sources of stem cells that would be genetically matched to particular patients--a significant number of eggs will be needed both to fuel the initial research and eventually to satisfy the demands of patients. Scientists at Advanced Cell Technology of Worcester, Mass. , made the decision to pay women only after a long analysis by an ethics board created by the company, said scientific director Robert Lanza. He still thinks it is the right way to go, Lanza said, given the painful injections involved, the uncomfortable egg suction procedure, and the approximately 5 percent chance of a serious case of hormonal over-stimulation, which can require hospitalization. Others say such payments cannot help but be coercive, especially for poor women who might feel compelled to take on those risks just to make ends meet. In April, the National Academies, chartered by Congress to advise the nation on matters of science, released a report that recommended against payments for human eggs beyond expenses incurred by the donors, in part because of the "sensitivities" inherent in the creation of embryos destined for destruction. But the report's impact remains uncertain as research institutions, fertility clinics and the biggest wild card of them all--Congress--mull the Academies' findings.

单选题He is such a ______ that he built a porch for his house last summer during his vacation. A. productive B. versatile C. authoritative D. solitary