Critical Reasoning

too poorly worded. Can't be on Gmat.

need720+ wrote: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

The answer is definitely D. The metals in the ground kills other plants, but not the herb. Why? theory is that the herb produces histidine, which makes the metal inert (so they don't hurt the herb). The conclusion is that the histidine is the cause of the herb's survival in metal-rich grounds. It's a causal argument - even if the histidine works in a lab, that alone does not mean that the histidine is the cause for the plant's survival in the field. You could weaken this conclusion showing that the histidine does not work outside of the lab, and that there's another cause for its survival - for example, by showing that it's not the histidine, but the herb's fibers are somehow metal-compatible. D strengthens the conclusion that the histidine mechanism is indeed the cause of survival because it shows that the histidine does what it's supposed to - it renders the metal inert so it does not affect the herb, or other plants who get to live there as well. Thus D strengthens the conclusion that histidine is the cause both by providing an example that the mechanism the argument talks about works, and by eliminating a potential weakener.

Conclusion: the herb's high histidine production is what allows it to grow in metal-rich soils
Strengthen:

C. others of the closely related group of plants are also found to produce histidine in large quantitiesAssumption: Same environment
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[ Not talking about histidine]Assumption: Metal decays totally
E. the concentration of histidine in the growing herb declines as the plant approaches maturity
[Growing herb cannot drop its histidine.. it opposes the entire para]

Hi Geva,
As per Ron, the answer is C.

See link: https://www.beatthegmat.com/cultivated-h ... 92-15.html

Now I am wondering what is the correct answer?

boazkhan wrote:Hi Geva,
As per Ron, the answer is C.

See link: https://www.beatthegmat.com/cultivated-h ... 92-15.html

Now I am wondering what is the correct answer?

Without the OA, I guess we'll never know.