新GRE小短文阅读练习题五十二

会计考友

Snail populations are dying off in certain European forests because acid
2 S1 e! E- X8 d* |rain has depleted the soil of nutrients the snails need.  These forests are
0 ]% M; u* f1 E7 y. N$ P! \the sole habitat of birds called passerines, which get most of the calcium
! h0 E+ o. u& G# A" G. M8 Othey need from snail shells.  When passerines get too little calcium, more
  y  c% J% K6 |7 D' P- @+ G: tof their eggs have abnormally thin shells, and, accordingly, fewer off-
1 y! A' @9 ?" V1 g8 b+ G. N9 d1 xspring survive.  Therefore, acid rain will probably cause a decrease in
the population of European passerines.
: p$ M% y% c" ], P Which of the following, if true, most strengthens the argument given?
& f% H9 V$ S2 l' E      A Nothing in the forests other than snail shells can provide passerines
  with calcium in the amount that they need.  
! Z3 f+ B' U  g" O3 A      B  Some cases of passerines laying eggs with very thin shells have
3 U0 h; {2 O3 I( f" m       been attributed to causes other than calcium deficiency.  
& Q5 G( q' S6 S& a     C When the population of passerines in a forest declines, populations
        of predatory birds that prey on passerines also tend to decline in
       that forest.  
! G; t0 ~3 \7 X     D If the acidity of rain in Europe were reduced, then nutrients in forest
       soils would be restored to earlier levels.  
+ c8 i: E2 w8 I7 ]) H! h     E Because of recent expansion of certain European forests, the amount
       of habitat suitable for passerines has increased.  
# f7 |0 Y5 K8 _- `' c答案A