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.

答案选A，我觉得应该选B。请指点迷津。

 B 说 SIMILAR 但不是SAME

A 说 "Prevention of the regeneration of damaged nerves is merely a by-product ",

说明此"nerve-growth inhibitors" 还有其他更多的作用. "deactivate those inhibitors"

可能导致其它的副作用.

但是选A的话，从"Prevention of the regeneration of damaged nerves is merely a

by-product "得到不能实现“nerve repair will be a standard medical procedure in the

foreseeable future”的结论必须基于一个假设，即："deactivate those inhibitors" 对身

体有害，而不是有益。

而B的assumption为：与antibodies against nerve-growth inhibitors 有相似化学结构的

nerve-growth stimulants有与antibodies相似的作用。

我觉得还是B的gap比较小，你觉得呢？

i think b not weaken but supports the conclusion.

b tells us that certain n-g stimulants not only can stimulate nerve to growth but also prove n-g inhibitors from inhibiting the n-g  to growth.

therefore b suppots the conclusion.

我认为B不是加强但是违反了白痴原则， 因为similar chemial structure 并不意味着相

似的作用

同意，B不是same,所以不会影响accuracy.

但是A，只是一个by-product，那么肯定会影响到main function，所以不accurate

我觉得毛病出在"nerve repair will be a standard medical procedure in the foreseeable future."这个结论里.

nerve repair未必特指"使用nerve-growth inhibitors",只要存在修复神经的方法(不论什么方法,也不论有多少种方法), 那么"神经修复"就会成为一个标准的医疗过程.

于是B就无法削弱结论. 因为就算有一种stimulant与nerve-growth inhibitor具有相同作用,也无法阻止"神经修复"成为标准过程,只不过是多了一种实现方法而已.
A就不同了,它直接置疑nerve-growth inhibitor的作用机理, 欲否定掉"神经修复"的唯一理论依据. 如果nerve-growth inhibitor有坏的作用,那么就算有作用类似的stimulator,也无法使"神经修复"成为一种可行的过程,更谈不上标准了.