XDF补充材料section19-6,19-15

6. Damaged nerves in the spinal cord do not regenerate themselves naturally, nor even under the spur of nerve-growth stimulants. The reason, recently discovered, is the presence of nerve-growth inhibitors in the spinal cord. Antibodies that deactivate those inhibitors have now been developed. Clearly, then, nerve repair will be a standard medical procedure in the foreseeable future.

  Which of the following, if true, casts the most serious doubt on the accuracy of the prediction above?
  (A) Prevention of the regeneration of damaged nerves is merely a by-product of the main
     function in the human body of the substances inhibiting nerve growth.
  (B) Certain nerve-growth stimulants have similar chemical structures to those of the antibodies
     against nerve-growth inhibitors.
  (C) Nerves in the brain are similar to nerves in the spinal cord in their inability to regenerate
     themselves naturally.
  (D) Researchers have been able to stimulate the growth of nerves not located in the spinal cord
     by using only nerve-growth stimulants.
  (E) Deactivating the substances inhibiting nerve growth for an extended period would require a
     steady supply of antibodies.

answer: A
A是什么意思？为什么选A？

15. Over the last century, paleontologists have used small differences between fossil specimens to classify triceratops into sixteen species. This classification is unjustified, however, since the specimens used to distinguish eleven of the species come from animals that lived in the same area at the same time.

   Which of the following, if true, would enable the conclusion of the argument to be properly drawn?
   (A) Not every species that lived in a given area is preserved as a fossil.
   (B) At least one individual of every true species of triceratops has been discovered as a fossil
      specimen.
   (C) No geographical area ever supports more than three similar species at the same time.
   (D) In many species, individuals display quite marked variation.
   (E) Differences between fossil specimens of triceratops that came from the same area are no
      less distinctive than differences between specimens that came from different areas.

answer: C     

why C?

thank you~

原来是这样呀 明白了 谢谢~~

脊髓里受损伤的神经不会自己天然的再生，也不会在神经增长刺激物的刺激下再生。最近发现的原因是对在骨髓里神经增长抑制剂的出现。现在能减弱那些抑制物活动的抗体已经被开发出来。然后，神经修补将是未来一个标准的医疗过程。

对预测的准确性的削弱。

对再生神经的抑制剂而言，它只是人体内阻止神经增长的物质在发挥主要功效时的副产品。（说明文章中提到的inhibitors只是真正起作用的物质的一个副产品，而真正起主要抑制作用的物质没有得到很好的控制，所以，文章的预测是被削弱。他因削弱。）

15 在过去的一个世纪，古生物学家使用非常细微的差别通过化石标本把三角龙分成16种。然而，这种分法是没被证实的，因为那些用来区分成11种的标本是来至同一时间同一地点的动物。
找假设，支持结论。
C 是一个很好的取非削弱项。削弱：在同一时间，地理位置的不同会支持多于三种类似种类的产生。（削弱了结论：同一时间同一地点的说法。）