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.（A）

(E) Deactivating the substances inhibiting nerve growth for an extended period would require a steady supply of antibodies.

为什么a削弱？

文章说的中的关系是不是Antibodies deactivate those inhibitors 而

inhibitors prevent the regeneration of damaged nerves

a说Prevention of the regeneration of damaged nerve是inhibtor的by-

product 没有削弱阿

原文的reasoning：the presence of nerve-growth inhibitors cause

Damaged nerves in the spinal cord do not regenerate --Antibodies that

deactivate those inhibitors have now been developed-->nerve repair will

be a standard medical procedure in the foreseeable future.

关键是这句话的结论，A说抑制毁坏神经再生仅仅是抑制人体神经生长物质对人体

作用主要功能的一个附属功能，那么原文的结论神经恢复将成为一个标准的医学

手续当然就不能确定了。