GWD 19-19 再求助！！！

wjd0315

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.

答案选D，可我觉得B也可以削弱啊~~~~
碰到GWD我真是不会了。。。请教各位！！！

sdcar2010

The hypothesis is: this shortage of iron prevents plankton from thriving.

Note the word SHORTAGE, which denotes a relative value.

Then look at choice B) Certain areas of the ocean support an abundance of plankton despite having particularly low concentrations of iron.

Here LOW does not equal a SHORTAGE. A low concentration of iron might just be sufficient for the organisms to survive.

wjd0315

哦~~谢谢SDCAR~~~理解了~~
可是为什么选D我也不太懂，能不能麻烦再解释一下啊？、
谢啦~~~~

兰心寒

wjd0315 发表于 2012-2-28 10:12
哦~~谢谢SDCAR~~~理解了~~可是为什么选D我也不太懂，能不能麻烦再解释一下啊？、谢啦~~~~ ...

O认为： This shortage of iron prevents plankton from thriving。
文章结论，以一个However,加实验结果，反驳O的认为，认为它是错的。
题目：argues most against the concluding,即削弱文章的结论。因为文章的结论是base在最后一个experiment的基础上，说O不对。那要削弱，我认为首先要考虑的就是这个experiment不能说明问题。
D选项恰恰说明了这点：你刚放进去的iron compound就被水流冲走了，你的结论就站不住脚了。
A是无关项， nitrogen compounds并不能说明什么，因为O's hypothesis只和iron有关。而认为O是错的的concluding中的experiment也只和iron有关
C说iron不能增加nitrogn compound,其实跟A为什么错一样。