笨笨求指教

Q28:
Which of the following most logically completes the argument?

A certain cultivated herb is one of a group of closely related plants that thrive in soil with high concentrations of metals that are toxic to most other plants.  Agronomists studying the herb have discovered that it produces large amounts of histidine, an amino acid that, in test-tube solutions, renders these metals chemically inert.  Possibly, therefore, the herb's high histidine production is what allows it to grow in metal-rich soils, a hypothesis that would gain support if ______.

A. histidine is found in all parts of the plant-roots, stem, leaves, and flowers
B. the herb's high level of histidine production is found to be associated with an unusually low level of production of other amino acids
C. others of the closely related group of plants are also found to produce histidine in large quantities
D. cultivation of the herb in soil with high concentrations of the metals will, over an extended period, make the soil suitable for plants to which the metals are toxic
E. the concentration of histidine in the growing herb declines as the plant approaches maturity

答案是啥？我选C

假设这种植物叫X，和它同属一个group里的closely related group of plants统称Y

题目得出的假设是：高分泌量的histidine是这种植物X能在高金属含量土壤里生存的原因。

作者推出假设的逻辑是：1）已知A能在高金属含量土壤里生存； 2）X分泌出大量的histidine，而这种东西能够使土壤里的金属保持”惰性“。由（1）和（2）共同推出假设。

答案C说Y也分泌出大量的histidine，根据（2）知道，这种东西能够使土壤里的金属保持”惰性“。而同（1）一样，Y也能在高金属含量土壤里生存，所以同样由（1）和（2）可以推出高分泌量的histidine是这种植物Y能在高金属含量土壤里生存的原因。

而Y又是X的”closely related group of plants“，所以Y的发现对X的结论也有支持作用。

A 说在X全身都发现了这种histidine。多并不代表有用哈，无法支持题目结论。

B 说X身上的histidine和另一种酸存在此消彼长的关系。这和题目结论完全没关系。

D 说经常一段时间发现X能改善土壤，使之毒害变低。这就好比题目说吃这种药可以抵抗流感，而D则说吃这种药可以杀死空气中的流感病毒...可是没提吃药的人还会不会得流感...

E 说X长大了histidine就变少了。和A一样，结论不是量的问题。这个无法支持题目的假设。