gwd 28-28, 请教

ershao

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.  ossibly, 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

答案是E,但 histidine浓度随着它成长过程的下降 能支持 istidine是导致herb在high-metal土壤中存活 这个假设么?

[此贴子已经被作者于2005-12-24 17:16:35编辑过]

五大老

这个题我也做错了，选的D，不知谁能讲一下

titatita

up

i vote for c

titatita

噢,我有些明白了,随着成熟h的逐渐水平下降,说明h一直在抑制着土壤里的metal

也就是说h由于用于一直metal,而一直下降.

其他四项都是无关选项.

titatita

今天再看我觉得选d

c无关

e随着herb的成熟,the concentration of histidine减少,可以理解为hitidine用于减少土壤的毒性,但也可以理解为只是减少,但并未对土壤毒素起作用,所以如果没有更好的选项是可以选e,

d经过一段时间,种植h的土壤可以适合原本会中毒的那些植物生长,非常直接地support了假设

hedge

thanks

hedge

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无关
3. others of the closely related group of plants are also found to produce histidine in large quantities无关
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
                   削弱

benja

觉得D有个地方不大合适，

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。

而文章已经说了：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

也即这个金属对于herb是无毒的

所以说D应该属于无关项

easylau

我也觉得是D。。。

因为这种herb产生的h可以抑制土壤里的metal，使得原本不能种植的plant也能够在这些土壤上生长，不是可以起到support的作用吗？为啥答案是E呀？