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[GRE模拟] 新GRE小短文阅读练习题五十二

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发表于 2012-8-15 12:40:43 | 显示全部楼层 |阅读模式
Snail populations are dying off in certain European forests because acid # `+ ?: w! }" H. S) B- s4 [* O- x' D
rain has depleted the soil of nutrients the snails need.  These forests are
( B, c0 K5 r" a9 m6 ~$ w/ i- bthe sole habitat of birds called passerines, which get most of the calcium . m1 }! \4 z6 y+ w6 W. Y
they need from snail shells.  When passerines get too little calcium, more # a3 h/ f0 q1 X' R6 P5 E4 y
of their eggs have abnormally thin shells, and, accordingly, fewer off-/ {" t& c: i8 Y1 y4 d8 B
spring survive.  Therefore, acid rain will probably cause a decrease in 1 Q4 m% r2 d6 B6 I: i4 d0 h9 D
the population of European passerines.
0 T4 V( f: S$ O% V* T9 S# ^- B; d6 {/ _9 c Which of the following, if true, most strengthens the argument given?
6 W' I) X4 D. q+ [: G) J; c' @      A Nothing in the forests other than snail shells can provide passerines
& w8 z$ s) A3 F, M! U: Y  with calcium in the amount that they need.  
8 p) _& J; C" j+ u      B  Some cases of passerines laying eggs with very thin shells have # o2 s/ G; _' D  H% e; y1 q
       been attributed to causes other than calcium deficiency.  ( r, N) u' f) o' G
     C When the population of passerines in a forest declines, populations ( q" E( e( J- z5 ~9 ^) ]& v8 B
        of predatory birds that prey on passerines also tend to decline in
2 v& {  t, B: {/ L       that forest.  + d) ~" U( [- m
     D If the acidity of rain in Europe were reduced, then nutrients in forest
# a" a7 r6 o2 A9 w  O& o, r       soils would be restored to earlier levels.  
5 C* c. T; E$ @4 _: F9 E! v     E Because of recent expansion of certain European forests, the amount
& r$ ^* J* P8 f       of habitat suitable for passerines has increased.  
# n2 b) a8 q8 E! f" r答案A
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