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Healthy lungs produce a natural antibiotic that protects them from inf

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Healthy lungs produce a natural antibiotic that protects them from inf  [#permalink]

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New post Updated on: 23 Jan 2019, 04:50
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Healthy lungs produce a natural antibiotic that protects them from infection by routinely killing harmful bacteria on airway surfaces. People with cystic fibrosis, however, are unable to fight off such bacteria, even though their lungs produce normal amounts of the antibiotic. The fluid on airway surfaces in the lungs of people with cystic fibrosis has an abnormally high salt concentration; accordingly, scientists hypothesize that the high salt concentration is what makes the antibiotic ineffective.

Which of the following, if true, most strongly supports the scientist's hypothesis?


(A) When the salt concentration of the fluid on the airway surfaces of healthy people is raised artificially, the salt concentration soon returns to normal.

(B) A sample of the antibiotic was capable of killing bacteria in an environment with an unusually low concentration of salt.

(C) When lung tissue from people with cystic fibrosis is maintained in a solution with a normal salt concentration, the tissue can resist bacteria.

(D) Many lung infections can be treated by applying synthetic antibiotics to the airway surfaces.

(E) High salt concentrations have an antibiotic effect in many circumstances.

Originally posted by marine on 20 Sep 2004, 06:25.
Last edited by Bunuel on 23 Jan 2019, 04:50, edited 2 times in total.
Edited the question.
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Re: Healthy lungs produce a natural antibiotic that protects them from inf  [#permalink]

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New post 13 Mar 2005, 22:44
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1) healthy lungs produce natural antibiotic

2) antibiotic protects lungs from infection by routinely killing harmful bacteria on airway surface

3) people with cystic fibrosis are unable to fight off bacteria, even when lungs produce normal amounts of antibiotics

4) Fluid on airway surfaces in lungs of people with cystic fibrosis has an abnormally high salt concentration

5) scientist hypothesize that high salt concentration is what makes the antibiotic ineffective <-- conclusion

We want an answer that supports the conclusion

A. When the salt concentration of the fluid on the airway surfaces of healthy people is raised artificially, the salt concentration soon returns to normal.
- Does not say salt concentration renders antibiotic ineffective

B. A sample of the antibiotic was capable of killing bacteria in an environment with an unusually low concentration of salt.
- Only supports low concentration salt premise

C. When lung tissue from people with cystic fibrosis is maintained in a solution with a normal salt concentration, the tissue can resist bacteria.
- This chioce supports the conclusion that high salt concentration in people with cystic fibrosis renders the antibiotic useless.

D. Many lung infections can be treated by applying synthetic antibiotics to the airway surfaces.
- Tells us nothing

E. High salt concentrations have an antibiotic effect in many circumstances.
- Negative effect or positive effect. Not stated here. E is out.

C it is.
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Re: Healthy lungs produce a natural antibiotic that protects them from inf  [#permalink]

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New post 13 Mar 2005, 22:46
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Between B and C, i went with C. B states that the antibiotic was effective in killing bacteria only in unusally low concentrations of salt. But do we know if a normal person has unusally low salt concentration ?? We do not, but we do know that their salt concentration would more or less be at a normal level. (whether this normal level is high or low does not matter, it's normal on the average). The word 'unusally' is too limiting.
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Re: Healthy lungs produce a natural antibiotic that protects them from inf  [#permalink]

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New post 14 Mar 2005, 00:48
clearly C for me

C. When lung tissue from people with cystic fibrosis is maintained in a solution with a normal salt concentration, the tissue can resist bacteria.

In my opinion :
B. A sample of the antibiotic was capable of killing bacteria in an environment with an unusually low concentration of salt.
no information at all, we just know the antibiotic can kill bacteria when there is a low concentration of salt however the issue raised here is only when there is a high salt concentration. So it's totally useless to know the action of the antibiotic in a low salt environnement. Moreover, choice B doesn't clearly precise whether the sample of the antobiotic is coming from people with cystic fibrosis or not...
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Re: Healthy lungs produce a natural antibiotic that protects them from inf  [#permalink]

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New post 14 Mar 2005, 00:51
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marine wrote:
Healthy lungs produce a natural antibiotic that protects them from infection by routinely killing harmful bacteria on airway surfaces. People with cystic fibrosis, however, are unable to fight off such bacteria, even though their lungs produce normal amounts of the antibiotic. The fluid on airway surfaces in the lungs of people with cystic fibrosis has an abnormally high salt concentration; accordingly, scientists hypothesize that the high salt concentration is what makes the antibiotic ineffective.

Which of the following, if true, most strongly supports the scientists’ hypothesis?

A. When the salt concentration of the fluid on the airway surfaces of healthy people is raised artificially, the salt concentration soon returns to normal.
B. A sample of the antibiotic was capable of killing bacteria in an environment with an unusually low concentration of salt.
C. When lung tissue from people with cystic fibrosis is maintained in a solution with a normal salt concentration, the tissue can resist bacteria.
D. Many lung infections can be treated by applying synthetic antibiotics to the airway surfaces.
E. High salt concentrations have an antibiotic effect in many circumstances.


C it is.

People with cystic fibrosis has an abnormally high salt concentration, and high salt concentration causes they cannot to fight off such bacteria.

Ask for support.

No high salt concentration makes people with cystic fibrosis be able to fight off such bacteria.

An typical question.

If A, then B. If not A, then not B.
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Re: Healthy lungs produce a natural antibiotic that protects them from inf  [#permalink]

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New post 14 Mar 2005, 06:19
I am torn between B and C. They seem to be both equally likely
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New post 14 Mar 2005, 08:38
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Folaa3 wrote:
I am torn between B and C. They seem to be both equally likely


Note also the use of 'unusally low salt cocentration' in (B). How low is low, we do not know.
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Re: Healthy lungs produce a natural antibiotic that protects them from inf  [#permalink]

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New post 01 Mar 2013, 07:11
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Agree with rsaraiya; C it is.

The conclusion is : high salt concentration is what makes the antibiotic ineffective to people with cystic fibresis

According to the argument :
Healthy lungs produce a natural antibiotic that protects them from infection
People with cystic fibrosis are unable to fight off such bacteria, even though their lungs produce normal amounts of the antibiotic
The fluid on airway surfaces in the lungs of people with cystic fibrosis has an abnormally high salt concentration
Now, let see the answer choices one by one :

A. When the salt concentration of the fluid on the airway surfaces of healthy people is raised artificially, the salt concentration soon returns to normal.
OUT OF SCOPE : We are concerned with people with cystic fibrosis not with people with healthy lungs.
B. A sample of the antibiotic was capable of killing bacteria in an environment with an unusually low concentration of salt.
doesn't mention people with cystic fibresis, hence this option does'nt strenghten the argument
C. When lung tissue from people with cystic fibrosis is maintained in a solution with a normal salt concentration, the tissue can resist bacteria.
Correct , this explains well why the antibiotic is ineffective while the salt concentration is HIGH because when normal , the antibiotic is known to be effective
D. Many lung infections can be treated by applying synthetic antibiotics to the airway surfaces.
the argument never mentioned synthetic antibiotic though it cannot be the correct answer
E. High salt concentrations have an antibiotic effect in many circumstances.
Clearly Irrelevant
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Re: Healthy lungs produce a natural antibiotic that protects them from inf  [#permalink]

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New post 31 May 2015, 20:40
Healthy lungs produce a natural antibiotic that protects them from infection by routinely killing harmful bacteria on airway surfaces. People with cystic fibrosis, however, are unable to fight off such bacteria, even though their lungs produce normal amounts of the antibiotic. The fluid on airway surfaces in the lungs of people with cystic fibrosis has an abnormally high salt concentration; accordingly, scientists hypothesize that the high salt concentration is what makes the antibiotic ineffective.

Which of the following, if true, most strongly supports the scientists' hypothesis?

Conclusion : high salt concentration is what makes the antibiotic ineffective

A. When the salt concentration of the fluid on the airway surfaces of healthy people is raised artificially, the salt concentration soon returns to normal
This option talks about that if the salt concentration of the fluid is brought up, the salt concentration returns to normal. This option doesn't provide any information why or how high salt concentration makes the antibiotic ineffective

B. A sample of the antibiotic was capable of killing bacteria in an environment with an unusually low concentration of salt.
This is as per premise that antibiotic is effective in low concentration of salt

C. When lung tissue from people with cystic fibrosis is maintained in a solution with a normal salt concentration, the tissue can resist bacteria.
Correct as it supports that if the salt concentration is brought back to normal, the natural antibiotic is effective.

D. Many lung infections can be treated by applying synthetic antibiotics to the airway surfaces.
Out of scope as we are not concerned with "Synthetic Antibiotics"

E. High salt concentrations have an antibiotic effect in many circumstances.
Out of scope as in many circumstances high salt concentrations have an antibiotic effect but we are concerned with this particular scenario
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Re: Healthy lungs produce a natural antibiotic that protects them from inf  [#permalink]

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New post 19 Mar 2018, 08:23
GMATNinja VeritasPrepKarishma GMATNinjaTwo

Can you please explain B / C?
Why do none of answer choices talk about high salt concentration?

I need to strengthen scientist's hypothesis which is: high salt concentration is one which makes the antibiotic ineffective.
What evidence I have?

Quote:
People with cystic fibrosis, however, are unable to fight off such bacteria, even though their lungs produce normal amounts of the antibiotic.


Some abnormality called CF makes people less immune in spite of sufficient quantity of antibiotics produced

Quote:
The fluid on airway surfaces in the lungs of people with cystic fibrosis has an abnormally high salt concentration;


The fluid in lungs of people with CF have very high salt concentration.

So author concludes that high salt concentration makes antibiotic ineffective and people less immune to bacteria.

Is below reasoning correct?
Cause: high salt concentration
Effect: anitibiotics are made ineffective

One way to strengthen A leads to B is:
No A -> no B

I think this is what (C) does.

For (B) can I assume it as same as premise since we are mentioned about :
high concentration makes antibiotic ineffective in argument
B says:
low concentration makes antibiotic effective in argument

Is not logical opposite of:
high concentration : normal concentration and low concentration?
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Re: Healthy lungs produce a natural antibiotic that protects them from inf  [#permalink]

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New post 23 Mar 2018, 19:00
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adkikani wrote:
GMATNinja VeritasPrepKarishma GMATNinjaTwo

Can you please explain B / C?
Why do none of answer choices talk about high salt concentration?

I need to strengthen scientist's hypothesis which is: high salt concentration is one which makes the antibiotic ineffective.
What evidence I have?

Quote:
People with cystic fibrosis, however, are unable to fight off such bacteria, even though their lungs produce normal amounts of the antibiotic.


Some abnormality called CF makes people less immune in spite of sufficient quantity of antibiotics produced

Quote:
The fluid on airway surfaces in the lungs of people with cystic fibrosis has an abnormally high salt concentration;


The fluid in lungs of people with CF have very high salt concentration.

So author concludes that high salt concentration makes antibiotic ineffective and people less immune to bacteria.

Is below reasoning correct?
Cause: high salt concentration
Effect: anitibiotics are made ineffective

One way to strengthen A leads to B is:
No A -> no B

I think this is what (C) does.

For (B) can I assume it as same as premise since we are mentioned about :
high concentration makes antibiotic ineffective in argument
B says:
low concentration makes antibiotic effective in argument

Is not logical opposite of:
high concentration : normal concentration and low concentration?

adkikani, your explanation of (C) sounds good! If we take away the cause (high salt concentration), the effect goes away. This suggests that high salt concentration was indeed the cause.

All (B) tells us is that an unusually low concentration of salt is NOT a problem. This does not necessarily suggest that an unusually high concentration would be a problem. What if salt concentration is irrelevant?
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Re: Healthy lungs produce a natural antibiotic that protects them from inf  [#permalink]

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New post 07 Jun 2019, 09:16
Healthy lungs produce a natural antibiotic that protects them from infection by routinely killing harmful bacteria on airway surfaces. People with cystic fibrosis, however, are unable to fight off such bacteria, even though their lungs produce normal amounts of the antibiotic. The fluid on airway surfaces in the lungs of people with cystic fibrosis has an abnormally high salt concentration; accordingly, scientists hypothesize that the high salt concentration is what makes the antibiotic ineffective.

Which of the following, if true, most strongly supports the scientists' hypothesis?

HIGH SALT CONCENTRATION (CAUSE)-----> ANTIBIOTIC TO BE INFFECTIVE(EFFECT)

Things to keep in mind when strengthening A CAUSAL RELATION

A. Eliminate any alternate causes for the stated effect
Because the author believes there is only one cause (the stated cause in the argument), eliminating other possible causes strengthens the conclusion.

B. Show that when the cause occurs, the effect occurs
Because the author believes that the cause always produces the effect, any scenario where the cause occurs and the effect follows lends credibility to the conclusion.This type of answer can appear in the form of an example.

C. Show that when the cause does not occur, the effect does not occur
Using the reasoning in the previous point, any scenario where the cause does not occur and the effect does not occur supports the conclusion. This type of answer also can appear in the form of an example.

D. Eliminate the possibility that the stated relationship is reversed
Because the author believes that the cause and effect relationship is correctly stated, eliminating the possibility that the relationship is backwards (the claimed effect is actually the cause of the claimed cause) strengthens the conclusion.

E. Show that the data used to make the causal statement are accurate, or eliminate possible problems with the data
If the data used to make a causal statement are in error, then the validity of the causal claim is in question. Any information that eliminates error or reduces the possibility of error will support the argument.


Now let us look at the answer choices :

A) This does not show any relationship between salt concentration and the functioning of the antibiotic.

B) Though the antibiotic was capable in killing bacteria in an environment where the salt concentration was unusually low, the choice does not say that in an environment where the salt concentration is high, the antibiotic will not be able to kill the bacteria.

C) CORRECT: since the environment created here has normal salt concentration and not high salt concentration, the point that high salt concentration in the lungs of such individuals is what has resulted in the antibiotic not being affected, is supported. Shows that when the cause does not occur, the effect does not occur

D)This does mention the cause for the malfunctioning of the antibiotic in patients of cystic fibrosis.

E) The answer does not strengthen the point that high salt concentration stops the antibiotic from killing bacteria.
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Re: Healthy lungs produce a natural antibiotic that protects them from inf   [#permalink] 07 Jun 2019, 09:16
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