D应该是典型的干扰选项。D可以说推出这种herb会改善metal毒性，但是和histidine毫无关联。而要支持的结论却是the herb’s high histidine production is what allows it to grow in metal-rich soils
A certain cultivated herb is one of a group of closely related plants that thrive in soil 从语法上看 thrive是复数形式，应该修饰a group of plants，就是说这一群closely related herb都可以生长在这种metal环境下。C说others of the closely related group of plants are also found to produce histidine in large quantities, 从the来看，就是说的这个closely related group，那么如果其他这个group里面的herb也抗金属毒性，并且也有大量histidine，就可以更有力的说明是histidine在起作用。
个人觉得应选E。 根据 lawyer在帖子http://forum.chasedream.com/GMAT_CR/thread-23688-1-1.html中所说，“把握结论，特别是它的具体性，特殊性”。 本题的结论是the herb’s high histidine production is what allows it to grow in metal-rich soils,所以hestidine production和（could）grow in metal-rich soils都要能被体现出，C只是说此植物可以产hestidine，D只是说了可以生长在土地上，没说是hestidine production使其可以生长。E则说明当hestidine production declines 时，植物就渐渐死去。不知道这样想对不对....
The sentence marked in RED below is the actual hypothesis.:
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 ______.
Now lets go through each option to see if it supports the hypothesis marked in RED in above argument.
A. histidine is found in all parts of the plant—roots, stem, leaves, and flowers - This does not indicate that the histidine is responsible for the growth of herb in metal-rich soils. So does not support the hypothesis 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 - Same as A. Reject... C. others of the closely related group of plants are also found to produce histidine in large quantities - Many guys picked up this option. Let me tell you why this is NOT the correct answer. The sentence simply indicates that other closely related group of plants also produce histidine in large quantities. This statement might be true, but it does not prove that histidine is indeed responsible for herb's growth in metal-rich soil. It might be possible that some other element is responsible for the growth of plants, which is not yet being discovered. So this statement does not provide any support to the hypothesis. 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 - huh(?!), REJECT.... I don't think you guys want an explanation for this? E. the concentration of histidine in the growing herb declines as the plant approaches maturity - BINGO!!!! Read the hypothesis again. It says that the histidine helps the plants to GROW in the metal-rich soil. This is the only option which talks about growth of the herb. If the histidine is only helping the plants to grow, then logically it is not even required once the plant is fully grown. Also, this is the only BEST answer we have. Remember (?) BEST IS NOT IDEAL?
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发表于 2008-3-15 17:15:00
