Healthy lungs produce a natural antibiotic that protects them from infection by routinely killing harmful bacteria on airway surfaces. People with cystic fibroses, however, are unable to fight off such bacteria, even though their lungs produce normal amounts of the antibiotic. Since the fluid on airway surfaces in the lungs of people with cystic fibrosis bas an abnormally high salt concentration, scientists hypothesize that in high salt environments the antibiotic becomes ineffective at killing harmful bacteria.
Which of the following, if it were obtained as an experimental result, would most decisively undermine the scientists' hypothesis?
A.Healthy lungs in which the salt concentration of the airway-surface fluid has been substantially increased are able to reestablish their normal salt concentration within a relatively short period of time.
B.The antibiotic produced by the lungs is effective at killing harmful bacteria even when salt concentrations are below levels typical of healthy lungs.
C.The salt concentration of the airway-surface fluid in the lungs of people who suffer from cystic fibrosis tends to return to its former high levels after having been reduced to levels typical of healthy lungs.
D.The lungs of people who suffer from cystic fibrosis are unable to fight off harmful bacteria even when the salt concentration is reduced to levels typical of healthy lungs.
E.The salt concentration in the airway-surface fluid of people whose lungs produce lower-than-average amounts of the antibiotic is generally much lower than that typical of healthy lungs.
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Premise: Healthy lungs produce antibiotic that kills harmful bacteriaNewaz111 wrote:Healthy lungs produce a natural antibiotic that protects them from infection by routinely killing harmful bacteria on airway surfaces. People with cystic fibroses, however, are unable to fight off such bacteria, even though their lungs produce normal amounts of the antibiotic. Since the fluid on airway surfaces in the lungs of people with cystic fibrosis has an abnormally high salt concentration, scientists hypothesize that in high salt environments the antibiotic becomes ineffective at killing harmful bacteria.
Which of the following, if it were obtained as an experimental result, would most decisively undermine the scientists' hypothesis?
A.Healthy lungs in which the salt concentration of the airway-surface fluid has been substantially increased are able to reestablish their normal salt concentration within a relatively short period of time.
B.The antibiotic produced by the lungs is effective at killing harmful bacteria even when salt concentrations are below levels typical of healthy lungs.
C.The salt concentration of the airway-surface fluid in the lungs of people who suffer from cystic fibrosis tends to return to its former high levels after having been reduced to levels typical of healthy lungs.
D.The lungs of people who suffer from cystic fibrosis are unable to fight off harmful bacteria even when the salt concentration is reduced to levels typical of healthy lungs.
E.The salt concentration in the airway-surface fluid of people whose lungs produce lower-than-average amounts of the antibiotic is generally much lower than that typical of healthy lungs.
Premise: Cystic fibrosis people produce normal amounts of the antibiotic BUT can't kill bacteria
Premise: Cystic fibrosis people have abnormally high salt concentration
Conclusion: high salt concentration prevents antibiotics from killing bacteria
In other words, the high salt concentration CAUSES the antibiotics to stop working.
This is a CAUSE AND EFFECT argument.
A) This has nothing to do with conditions in which antibiotics don't work. ELIMINATE A
B) This doesn't hurt the argument. It says that antibiotics work in low salt concentrations. The conclusion concerns the notion that high salt concentration prevents antibiotics from working. ELIMINATE B
C) This has nothing to do with the effect that salt concentration has on antibiotic effectiveness. ELIMINATE C
D) This says that, if we reduce the salt concentration (of cystic fibrosis people), the antibiotics still don't work. So, it's not the salt concentration. There must be another factor in cystic fibrosis people that prevents antibiotics from working. KEEP D
E) This talks about the relationship between the AMOUNTS of antibiotics and salt concentration. It has nothing to do with the effectiveness of the antibiotics to do their job. ELIMINATE E
Answer: D
Cheers,
Brent