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Fluoride enters a region's groundwater when rain dissolves fluoride

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Fluoride enters a region's groundwater when rain dissolves fluoride  [#permalink]

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New post 30 Apr 2018, 12:07
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A
B
C
D
E

Difficulty:

  65% (hard)

Question Stats:

54% (01:48) correct 46% (01:46) wrong based on 203 sessions

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Fluoride enters a region's groundwater when rain dissolves fluoride-bearing minerals in the soil. In a recent study, researchers found that when rainfall, concentrations of fluoride-bearing minerals, and other relevant variables are held constant, fluoride concentrations in groundwater are significantly higher in areas where the groundwater also contains a high concentration of sodium.

Which one of the following can most reasonably be concluded on the basis of the researchers' findings?

(A) Fluoride-bearing minerals are not the primary source of fluoride found in groundwater.
(B) Rainfall does not affect fluoride concentrations in groundwater.
(C) Sodium-bearing minerals dissolve at a faster rate than fluoride-bearing minerals.
(D) Sodium in groundwater increases the rate at which fluoride-bearing minerals dissolve.
(E) Soil that contains high concentrations of sodium-bearing minerals also contains high concentrations of fluoride-bearing minerals.

Source: LSAT

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Re: Fluoride enters a region's groundwater when rain dissolves fluoride  [#permalink]

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New post 30 Apr 2018, 22:38
(A) Fluoride-bearing minerals are not the primary source of fluoride found in groundwater. -
No information on primary source. Irrelevant

(B) Rainfall does not affect fluoride concentrations in groundwater. - It does as stated in the argument. Incorrect.

(C) Sodium-bearing minerals dissolve at a faster rate than fluoride-bearing minerals.
- It is not about comparison b/w sodium bearing and fluoride bearing minerals. Irrelevant

(D) Sodium in groundwater increases the rate at which fluoride-bearing minerals dissolve.
- this concludes well taking into consideration the premise. Correct

(E) Soil that contains high concentrations of sodium-bearing minerals also contains high concentrations of fluoride-bearing minerals. - We are not talking about soil. Neither does it conclude well from the premise.

IMO D.

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Re: Fluoride enters a region's groundwater when rain dissolves fluoride  [#permalink]

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New post 17 May 2018, 09:22
We need to take into account things which Are already mentioned in passage.no new element is required

A) Fluoride-bearing minerals are not the primary source of fluoride found in groundwater.
primary source-new element so out [/]

(B) Rainfall does not affect fluoride concentrations in groundwater.[b] its too strong.we are not sure about this as we have info only when rainfall held constant


(C) Sodium-bearing minerals dissolve at a faster rate than fluoride-bearing minerals.not sure as we know where flouride is max sodium also max but whether sodium dissolve more nor not.cant say

(D) Sodium in groundwater increases the rate at which fluoride-bearing minerals dissolve.where flouride max ,so sodium max. So there can be reason that sodium help in some way to max flouride.lets keep it

(E) Soil that contains high concentrations of sodium-bearing minerals also contains high concentrations of fluoride-bearing minerals.last sentence says where flouride max, sodium max but vice versa we can't say so out

So best choice we have is D

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Re: Fluoride enters a region's groundwater when rain dissolves fluoride  [#permalink]

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New post 17 Oct 2018, 08:10
Hi Experts!

I can't understand this argument as it says in the premise that in the research "concentrations of fluoride-bearing minerals, and other relevant variables are held constant," - means rainfail did not actually dissolve the flouride-bearing minerals yet if the groundwater contains a high concentration of sodium, the flouride concentration is significantly higher.

I cannot come up with the logic of answer D which states that the sodium level increases at the rate of flouride dissolving. How could we conclude that?

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Re: Fluoride enters a region's groundwater when rain dissolves fluoride  [#permalink]

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New post 20 Oct 2018, 01:24
Can someone please tell how D is correct in the context of E being incorrect

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Re: Fluoride enters a region's groundwater when rain dissolves fluoride &nbs [#permalink] 20 Oct 2018, 01:24
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Fluoride enters a region's groundwater when rain dissolves fluoride

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