LSAT 136 | Section 2 | Logical Reasoning: Q5

LR Question 5 Explanation

QUESTION TEXT: Bacteria that benefit human beings when they are present…

QUESTION TYPE: Weaken

CONCLUSION: We shouldn’t consider H. pylori a commensal.

REASONING: H. Pylori harms 10% of the people who have it (though it also helps their immune systems). Mycobacter tuberculosis only harms 10% of the people who have it and no one would consider it a commensal.

ANALYSIS: This isn’t a good argument. H. pylori has some good and bad effects. We’re not told whether Mycobacter tuberculosis has any good effects.

H. pylori was considered a commensal precisely because it had good effects.

___________

1. This actually slightly strengthens the idea that H. pylori is a commensal. Its negative effects can be treated. That makes it more likely to have a beneficial effect overall.
2. You know, I’d rather have a cold that lasted a long while than gangrene that only lasted a few days. Length of illness isn’t everything.
3. CORRECT. This shows there is a major difference between the two bacteria. There’s absolutely no reason to consider Mycobacter tuberculosis a commensal, because it doesn’t help us and only hurts us. H. pylori does help us.
4. Whether we consider H. pylori a commensal depends on its effects, not how common it is.
5. Same as D.