In July of 1994, an astounding series of events took place. The world anxiously
    watched as, every few hours, a hurtling chunk of comet plunged into the atmosphere of
    Jupiter. All of the twenty-odd fragments, collectively called comet Shoemaker-Levy 9
Line after its discoverers, were once part of the same object, now dismembered and strung out
(5)  along the same orbit. This cometary train, glistening like a string of pearls, had been first
    glimpsed only a few months before its fateful impact with Jupiter, and rather quickly
    scientists had predicted that the fragments were on a collision course with the giant
    planet. The impact caused an explosion clearly visible from Earth, a bright flaming fire
    that quickly expanded as each icy mass incinerated itself. When each fragment slammed
(10) at 60 kilometers per second into the dense atmosphere, its immense kinetic energy was
    transformed into heat, producing a superheated fireball that was ejected back through the
    tunnel the fragment had made a few seconds earlier. The residues form these explo-
    sions left huge black marks on the face of Jupiter, some of which have stretched out to
    from dark ribbons.
(15)  Although this impact event was of considerable scientific importance, it especially piqued
    public curiosity and interest. Photographs of each collision made the evening television
    newscast and were posted on the Internet. This was possibly the most open scientific
    endeavor in history. The face of the largest planet in the solar system was changed before
    our very eyes. And for the very first time, most of humanity came to fully appreciate the
(20) fact that we ourselves live on a similar target, a world subject to catstrophe by random
    assaults from celestial bodies. That realization was a surprise to many, but it should not
    have been. One of the great truths revealed by the last few decades of planetary explo-
    ration is that collisions between bodies of all sizes are relatively commonplace, at least in
    geologic terms, and were even more frequent in the early solar system.
 
3. The author compares the fragments of comet Shoemaker-Levy 9 to all of the following EXCEPT
  (A) a dismembered body
  (B) a train
  (C) a pearl necklace
  (D) a giant planet
答案：D

      By far the most important United States export product in the eighteenth and
    nineteenth centuries was cotton, favored by the European textile industry over flax or
    wool because it was easy to process and soft to tile touch. Mechanization of spinning and
Line weaving allowed significant centralization and expansion in the textile industry during
(5)  this period, and at the same time the demand for cotton increased dramatically. American
    producers were able to meet this demand largely because of tile invention of the cotton
    gin by Eli Whitney in 1793. Cotton could be grown throughout the South, but separating
    the fiber—or lint—from the seed was a laborious process. Sea island cotton was
    relatively easy to process by hand, because its fibers were long and seeds were
(10) concentrated at the base of the flower, but it demanded a long growing season, available
    only along the nation's eastern seacoast. Short-staple cotton required a much shorter
    growing season, but the shortness of the fibers and their mixture with seeds meant that a
    worker could hand-process only about one pound per day. Whitney's gin was a hand-
    powered machine with revolving drums and metal teeth to pull cotton fibers away from
(15) seeds. Using the gin, a worker could produce up to 50 pounds of lint a day. The later
    development of larger gins, powered by horses, water, or steam, multiplied productivity
    further.
      The interaction of improved processing and high demand led to the rapid spread of
    the cultivation of cotton and to a surge in production. It became the main American
(20) export, dwarfing all others. In 1802, cotton composed 14 percent of total American
    exports by value. Cotton had a 36 percent share by 1810 and over a 50 percent share in
    1830. In 1860, 61 percent of the value of American exports was represented by cotton.
      In contrast, wheat and wheat flour composed only 6 percent of the value of American
    exports in that year. Clearly, cotton was king in the trade of the young republic. The
(25) growing market for cotton and other American agricultural products led to an
    unprecedented expansion of agricultural settlement, mostly in the eastern half of the
    United States—west of the Appalachian Mountains and east of the Mississippi River.
 
3. All of the following are mentioned in the passage as reasons for the increased demand for cotton EXCEPT
  (A) cotton's softness
  (B) cotton's ease of processing
  (C) a shortage of flax and wool
  (D) the growth that occurred in the textile industry.
答案：C