28-19: Plankton generally thrive in areas of the ocean with

sufficient concentrations of certain nitrogen compounds near the

surface where plankton live. Nevertheless, some areas, though rich

in these nitrogen compounds, have few plankton. These areas have

particularly low concentrations of iron, and oceanographers

hypothesize that this shortage of iron prevents plankton from

thriving. However, an experimental release of iron compounds into

one such area failed to produce a thriving plankton population,

even though local iron concentrations increased immediately.

Which of the following, if true, argues most strongly against

concluding, on the basis of the information above, that the

oceanographers’ hypothesis is false?

A: Not all of the nitrogen compounds that are sometimes found in

relatively high concentrations in the oceans are nutrients for

plankton.

B: Certain areas of the ocean support an abundance of plankton

despite having particularly low concentrations of iron.

C: The release of the iron compounds did not increase the supply of

nitrogen compounds in the area.

D: A few days after the iron compounds were released, ocean

currents displaced the iron-rich water from the surface.

E: The iron compounds released into the area occur naturally in

areas of the ocean where plankton thrive.

求问此题的思路.

我的问题是：

1. 被问题搅糊涂：Which of the following, if true, argues most

strongly against concluding, on the basis of the information above,

that the oceanographers’ hypothesis is false? 文中先出现了

oceanographers' hypothesis, 然后author提出疑问反对此 hypothesis. 问

题问的是不是反对author 的结论，也就是相当于削弱题？

2. C错在哪里？

自己先顶一下。

另外加问 同套题中的第28题

28-28: 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

看网上讨论的答案为E，我选D。也想看大家的讨论。谢谢！