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 nervegrowth 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 nervegrowth stimulants.
E．(E) Deactivating the substances inhibiting nerve growth for an extended period would require a steady supply of antibodies.
参考答案：A
解析： 本题属于“反对”题型。段落推理是：神经修复将成为可能，因为人们已开发出降低神经生长抑制剂活性的抗体。反对重点反对原因。如果防止受损神经的再生只是抑制神经生长的物质的主要功能的一个副作用，正如(A)所说，那么开发出降低神经生长抑制剂活性的抗体将消除神经生长抑制剂的主要功能，从而带来不利影响，因此结论必然不成立，所以(A)正确；(B)、(C)为无关比较；(D)的“不在脊髓内”与推理无关；(E)对上面推理起不到任何作用。