请大家指点，谢谢！Passage 67 (4/22)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 (leak out: v.泄漏) 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 (rain down: v.大量降下) on the surface of the neutron star, the temperature rises, until with a blinding flash of radiation, the collapse is reversed. A thermonuclear (thermonuclear: adj.高热原子核反应的) 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 (for the most part: adv.在极大程度上), 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 (cosmic rays: n. 宇宙线，宇宙射线). 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. 3. According to the passage all of the following are true of supernovas EXCEPT that they (A) are extremely bright (B) are an explosion of some sort (C) emit large quantities of X-rays (D) result in the destruction of a neutron star（E） (E) are caused by the collision of large galaxies 这一题选E没有问题，但是请问D的定位在哪里？怎么没找到neutron star是destructed的了。。 5. It can be inferred from the passage that the meteorites mentioned by the author at line 39 (A) contain dangerous concentrations of radioactive materials (B) give off large quantities of X-rays (C) include material not created in the normal development of our solar system (D) are larger than the meteors normally found in a solar system like ours（C） (E) contain pieces of a supernova that occurred several billion years ago 这一题彻底不明白，原文的the cloud与meteorites有什么关系吗？ | 
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发表于 2007-4-15 00:05:00
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