新东方逻辑178

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 toxic to most other plants. A gronomist 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_____.

D. cultivation of the herb in soil with high concentrations of the metals will, over an extened 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 plantapproaches maturity.

The answer is E, but I choose D because of the words bolded. I need your help.

Its quite tricky.

If E is true, when the herb approaches maturity, which also means it stops growing, the production of histidine gets weak

conclusion: histodine decides whether the herb grows or not

The maturity and declining take place at the same time, it would support that histodine is a must.

D saying the herb helps to lower the effect of metals, nothing to do with its growth needed in the conclusion.

不同意一点， 假如说人变老的时候，牙就变少了，不能说牙变少决定人变老吧。充分必要的问题。 另一个选项是b 说同类的植物也含有这种物质。我倾向于这个答案， 等待讨论。