raghavs wrote:
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.
This question is a little twisted so you have to make sure you understand it well.
Which of the following, if true, argues most strongly against concluding, on the basis of
the information above, that the
oceanographers’ hypothesis is false?
oceanographers’ hypothesis - oceanographers hypothesize that this shortage of iron prevents plankton from thriving
argues against concluding that above is false. So you have to argue against hypothesis being false - in effect - you have to argue that
the hypothesis might still be true. So look for something that says that the hypothesis could still be true and it could still be the missing iron that is the cause of low plankton population.
So you are looking for missing iron explanation.
D tells you that iron is still missing because it got displaced. That's the answer.
E could actually be part-basis of the hypothesis. It doesn't say why the hypothesis may still be true.