In July of 1994, an astounding series of events took place. The world anxiously
2 m2 [( e: U1 C watched as, every few hours, a hurtling chunk of comet plunged into the atmosphere of. ]4 {5 C) H; f' b. t
Jupiter. All of the twenty-odd fragments, collectively called comet Shoemaker-Levy 9+ ?/ t1 i- {/ ^6 m0 n O9 d* v' f
Line after its discoverers, were once part of the same object, now dismembered and strung out' V, W; l- J x& N' C
(5) along the same orbit. This cometary train, glistening like a string of pearls, had been first
7 f% }( z, S( o1 R6 v6 f glimpsed only a few months before its fateful impact with Jupiter, and rather quickly* Y+ _. d% @& p/ N! d$ I" |; A
scientists had predicted that the fragments were on a collision course with the giant
3 Y1 @" H" T; N& O2 U0 ^: b planet. The impact caused an explosion clearly visible from Earth, a bright flaming fire0 d3 S9 q, ? _
that quickly expanded as each icy mass incinerated itself. When each fragment slammed, q; i: {0 J5 j
(10) at 60 kilometers per second into the dense atmosphere, its immense kinetic energy was0 |2 ?* B/ z# I. h
transformed into heat, producing a superheated fireball that was ejected back through the- f. m* i: _) L0 T8 `
tunnel the fragment had made a few seconds earlier. The residues form these explo-
B3 a* q) |3 B9 j' K& Q sions left huge black marks on the face of Jupiter, some of which have stretched out to
P# |" ]" @# m1 M from dark ribbons.
& J; i: @; {0 h (15) Although this impact event was of considerable scientific importance, it especially piqued
1 U1 Q; L$ m7 X/ b public curiosity and interest. Photographs of each collision made the evening television
+ S1 ^! p9 v8 V9 R1 y" x newscast and were posted on the Internet. This was possibly the most open scientific: _0 W/ E7 W# U% D1 p# x
endeavor in history. The face of the largest planet in the solar system was changed before# y+ A* A0 Q' h4 ^8 j' f. M/ e
our very eyes. And for the very first time, most of humanity came to fully appreciate the) m5 e" w+ a# q2 g- o
(20) fact that we ourselves live on a similar target, a world subject to catstrophe by random$ \3 ?5 D9 U% j6 a
assaults from celestial bodies. That realization was a surprise to many, but it should not
+ ?( _6 @/ x2 O have been. One of the great truths revealed by the last few decades of planetary explo-0 n6 i- f* P1 L% c+ S1 i
ration is that collisions between bodies of all sizes are relatively commonplace, at least in, w# N3 H7 v) z5 h* \# u
geologic terms, and were even more frequent in the early solar system.
0 X! K5 G% W6 _: e 3. The author compares the fragments of comet Shoemaker-Levy 9 to all of the following EXCEPT
# _- K0 ~5 ~/ N% a6 Z (A) a dismembered body
3 z y0 c! K. E (B) a train
9 W& t( J$ ]" b0 X, S (C) a pearl necklace' r4 h* T1 R+ e+ V. T
(D) a giant planet
+ H2 Q1 z( }4 B6 u4 b. R 答案:D
0 s. p! O% e1 h& O5 Y4 } By far the most important United States export product in the eighteenth and/ X# ^4 o1 c+ S) x4 Y
nineteenth centuries was cotton, favored by the European textile industry over flax or
" g y4 r1 I/ |+ ^& J: v wool because it was easy to process and soft to tile touch. Mechanization of spinning and# n- N/ v1 Z1 ^5 ]; k% f
Line weaving allowed significant centralization and expansion in the textile industry during
& }0 G4 L( a4 U+ j4 f (5) this period, and at the same time the demand for cotton increased dramatically. American$ A" ^; o4 T/ K' i
producers were able to meet this demand largely because of tile invention of the cotton
& r' |; Z# k. Y& V gin by Eli Whitney in 1793. Cotton could be grown throughout the South, but separating
9 a6 F1 q+ C- J' ]" \$ c the fiber—or lint—from the seed was a laborious process. Sea island cotton was: u8 s" g6 t% i9 @8 q6 _( O/ t% Y) z
relatively easy to process by hand, because its fibers were long and seeds were6 V. ]% ], B6 G6 L6 V
(10) concentrated at the base of the flower, but it demanded a long growing season, available1 d/ V; M; z) }# v7 y2 K
only along the nation's eastern seacoast. Short-staple cotton required a much shorter
, x8 ? u' N8 v! x! v growing season, but the shortness of the fibers and their mixture with seeds meant that a X7 r5 w/ |, `' N7 E
worker could hand-process only about one pound per day. Whitney's gin was a hand-. X% x/ R% R* f; e# { f% O
powered machine with revolving drums and metal teeth to pull cotton fibers away from5 C" ]# H3 C$ f* E& }* K( x* r; W4 s
(15) seeds. Using the gin, a worker could produce up to 50 pounds of lint a day. The later1 V2 x2 C4 |' p1 \; q6 O! Q: m4 y
development of larger gins, powered by horses, water, or steam, multiplied productivity6 K* l: F8 h4 Q& J9 h( c B, [5 a
further.9 Y" j" @8 l1 _$ y
The interaction of improved processing and high demand led to the rapid spread of
) h0 ^5 F0 r/ B7 J% _. ` the cultivation of cotton and to a surge in production. It became the main American( t5 c7 V T3 i- B) a
(20) export, dwarfing all others. In 1802, cotton composed 14 percent of total American
6 R3 I0 E w' r; M; F' F exports by value. Cotton had a 36 percent share by 1810 and over a 50 percent share in
6 j( H4 N! C! @4 P3 D1 O 1830. In 1860, 61 percent of the value of American exports was represented by cotton.9 @$ }4 X( q) o
In contrast, wheat and wheat flour composed only 6 percent of the value of American+ O9 d. w+ p) x
exports in that year. Clearly, cotton was king in the trade of the young republic. The
4 I0 W0 `$ d) L f( Y (25) growing market for cotton and other American agricultural products led to an
8 P V' |0 t( ?* w+ ?* y; s& O unprecedented expansion of agricultural settlement, mostly in the eastern half of the. T# m4 Z8 F+ {. @6 b
United States—west of the Appalachian Mountains and east of the Mississippi River.
( C9 g' f# t2 h" o& o4 ^ 3. All of the following are mentioned in the passage as reasons for the increased demand for cotton EXCEPT! _- B0 @+ f- E2 I F
(A) cotton's softness
7 ~, y/ w) ]! P! [" z (B) cotton's ease of processing- b8 [6 @8 j& b. {; a l; m% Y. s
(C) a shortage of flax and wool8 x6 X# f0 T) h* B+ y3 p
(D) the growth that occurred in the textile industry.! A+ K, X2 S, O+ w$ U F
答案:C |