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板凳
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发表于 2017-3-26 13:27:16
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OA:
Situation A certain herb and closely related species thrive in soil full of metals toxic to
most plants. The herb produces much histidine, which makes those metals chemically
inert. Histidine production, therefore, is largely what accounts for the herb’s thriving in
metal-rich soils.
Reasoning What evidence would help determine whether the herb’s histidine production
is what enables it to thrive in metal-rich soils? The argument is that since the herb’s
histidine chemically neutralizes the metals that are toxic to most plants, it must explain
why the herb can thrive in metal-rich soils. To evaluate this argument, it would be helpful
to know about the relationship between other closely related plant species’ histidine
production and the ability to thrive in metal-rich soils. It would also be helpful to know
about any other factors that might plausibly explain why the herb can thrive in those soils.
A. Whether or not the herb thrives in metal-free soils, histidine production could
enable it to thrive in soils that contain toxic metals.
B. Correct. If the closely related plants do not produce much histidine, whatever other
factor allows them to thrive in metal-rich soils would likely account for why the herb
thrives in those soils as well.
C. The given information suggests no particular reason to suppose that a low level of
some unspecified amino acid would enable a plant to thrive in metal-rich soils.
D. The herb might absorb metals from any metal-rich soil it grows in, regardless of why
it thrives in that soil.
E. Whether or not histidine concentrations in the herb decline as it approaches
maturity, there could still be enough histidine in the growing herb to neutralize the
metals and explain why it can grow in metal-rich soil. |
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