如今JJ里面GWD28-Q28题，逻辑一题，哪个答案更好？

本月有人考到这个逻辑题目，哪个答案更好呀？C？,E？

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

觉得C是正确答案，要证明therefore后面的high histidine使得植物可以生长在metal-rich soils中，可以从C中找到support。因为其他类似植物（能生长于metal-rich soil中）也产生大量的high histidine，那就证明有可能存在的共性。

E是irrelevent的吧。