1.         GWD-28-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 ______.

A: histidine is found in all parts of the plant – roots, stem, leaves, and flowers

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

C: others of the closely related group of plants are also found to produce histidine in large quantities

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

E: the concentration of histidine in the growing herb declines as the plant approaches maturity

我选D。。

没什么可争议的

A: histidine is found in all parts of the plant – roots, stem, leaves, and flowers （浑身都是也没用，浑身是黄的不说明黄的能抗毒） 

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 （别的酸多少没关系）

C: others of the closely related group of plants are also found to produce histidine in large quantities
            

（类比，就比如发现有一组动物被蛇咬了都不会死，A是其中的一个，试验表明A的血液里有很多X蛋白，X蛋白在实验室里可以抑制蛇毒，问X蛋白是不是抗毒的原因呢？而后又发现那组动物统统都有X蛋白，自然结论得到了加强）

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

（结论并不是说这个herb能解毒，而是说histidine是抗毒的原因） 

E: the concentration of histidine in the growing herb declines as the plant approaches maturity （文中未提到herb成熟与抗毒能力的关系）

how about this one: thanks.

1.         GWD-31-Q17

It is crucially important to farmers that the herbicides they use to control weeds not (?) damage their crops. One very effective herbicide is safe for corn, but soybeans are damaged even by the herbicide’s residue, which remains in the soil more than a year after the herbicide is applied. Soybeans and corn are not sown together in the same filed; nevertheless, most farmers are reluctant to use the herbicide on their corn.

Which of the following, if true, provides the strongest justification for the farmers’ reluctance?

A: The residue of the herbicide in the soil a year after application is not enough to control most weeds effectively.

B: To maintain the nutrients in the soil, corn and soybeans are often planted in a field in alternate years.

C: The demand for soybeans is growing faster than is the demand for corn.

D: For maximum yield, soybean plants are grown closer together to each other than are corn plants.

E: The application of herbicides is less critical for soybean than for corn crops.