GWD28-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 ______.

1. histidine is found in all parts of the plant—roots, stem, leaves, and flowers
2. the herb’s high level of histidine production is found to be associated with an unusually low level of production of other amino acids
3. others of the closely related group of plants are also found to produce histidine in large quantities
4. 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
5. the concentration of histidine in the growing herb declines as the plant approaches maturity

我选D，有答案选C或者E，请大牛指点一二。多谢！

C选项的意思就是该样本的特点在整个样本空间中具有普遍性，所以support，应为正确答案。

D选项只是说明herb可以absorb这个metal，但是没有说明histidine在这个过程中的作用，为无关选项。

E选项说明了一个在plant生长过程中的事实，但不能证明histidine是因为与metal发生了作用而减少，也是无关选项。