单选题Landslides triggered by heavy rainfall Uimpeded/U our best attempts at rescuing the victims.

单选题"Our life is ______ away by detail. Simplify, simplify." That dictum of Henry David Thorean's, echoing from the days of steamboats and ox-drawn plows, had long haunted me. A. frittered B. quenched C. reproached D. scouted

单选题Shyness, the most common form of social anxiety, occurs when a person"s apprehensions are so great that they inhibit his making an expected or desired social response.

单选题{{B}}Passage Three{{/B}} There are hidden factors which scientists call "feedback mechanisms". No one knows quite how they will interact with the changing climate. Here's one example: plants and animals adapt to climate change over centuries. At the current estimate of half a degree centigrade of warming per decade, vegetation may not keep up. Climatologist James Hansen predicts climate zones will shift toward the poles by 50 to 75 kilometers a year--faster than trees can naturally migrate. Species that find themselves in an unfamiliar environment will die. The 1000-kilometer-wide strip of forest running through Canada, Russia, and Scandinavia could be cut by half. Millions of dying trees would soon lead to massive forest fires, releasing tons of CO2 and further boosting global warming. There are dozens of other possible "feedback mechanisms". Higher temperatures will fuel condensation and increase cloudiness, which may actually damp down global warming. Others, like the "albedo" effect is the amount of solar energy reflected by the earth's surface. As northern ice and snow melts and the darker sea and land pokes through, more heat will be absorbed, adding to the global temperature increase. Even if we were to magically stop all greenhouse-gas emissions tomorrow the impact on global climate would continue for decades. Delay will simply make the problem worse. The fact is that some of us are doing quite well the way things are. In the developed world prosperity has been built on 150 years of cheap fossil fuels. Material progress has been linked to energy consumption. Today 75 percent of all the world's energy is consumed by a quarter of the world's population. The average rich-world resident adds about 3.2 tons of CO2 yearly to the atmosphere, more than four times the level added by each Third World citizen. The US, with just seven percent of the global population, is responsible for 22 percent of global warming.

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You should be relieving me of duty at 10: 30, but don't hurry if it's inconvenient; I'll hang on till you arrive.

单选题Bill couldn't ______ an answer when the teacher asked him why he was late. A. come up with B. come over C. come on D. come up to

单选题Peterson found himself more and more ______ in the study of ancient Chinese art.

单选题They worked for three days in ______ without feeling tried. A successive B. succession C. succeeding D. successful

单选题The argument that children are no longer an economic asset, but more of a liability, drew more attention of the public.

单选题Which of the following can be the best title for the passage?

单选题Grand Teton National Park______ the most scenic portion of the glaciated, snow-covered Teton Range. A. excludes B. fulfils C. dominates D. expanding

单选题Which of the following is Not a perceived advantage of alliances?

单选题The patient has been ______ of the safety of the operation.

单选题Preferential policies and ready cooperation do play a role in ______ poverty.

单选题The massacre of innocent people cannot ever be Ucondoned/U.

单选题The armor, infantry and (other military forces) (were held up) by (the enemy counter attack), thus (caused) the delay in the advance.