蓝皮书 没讨论过的题

176. Plankton generally thrive in areas of ocean with sufficient concentrations of certain nitrogen compounds near the surface, wher plankon live. Nevertheless, some areas, though rich in these nitrogen compunds, have few plankton. These ares have particular 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 are failed produce a thriving plankton population, even though local iro concertrations 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 compunds were relased, ocean currents displaced the iron-rich water from the surface.

E. The iron compounds released into the are occur naturally in areas of the ocean where planton thrive.

E is the best?