#23 - Certain bacteria that produce hydrogen sulfide as a

[jonwg5121]

Can you please explain how to approach #23? I was able to eliminate (B) and (E) confidently.

I ended up choosing (C) although the answer was (A). I eliminated (A) because I thought the stimulus did not mention the bacteria indefinitely continuing to produce hydrogen sulfide. I eliminated (D) because of the word "only" and thought the conditional statement was wrong.

Thank you.

[Steve Stein]

Hi Jon,

Since this is a Must Be True question, the correct answer choice will be the one that passes the Fact Test and can be confirmed by the information provided in the stimulus. In that one, the author provides that the bacteria in question produce hydrogen sulfide, which removes oxygen and kills other bacteria. In so doing, that author says that a dense colony of such bacteria can continue to thrive indefinitely.

The author specifies that a dense colony of that bacteria can thrive indefinitely, implying that sufficient quantities of hydrogen sulfide can be produced to remove oxygen and kill other bacteria indefinitely.

I hope that's helpful! Please let me know whether this is clear--thanks!

~Steve

[DlarehAtsok]

Why is D) wrong?

[Adam Tyson]

Because, DlarehAtsok, the stimulus does not support the claim that ALL the oxygen must be removed and ALL other organisms have been killed. It could be that some oxygen remains but is kept out of direct contact with the bacteria, and some other organisms could survive in the area so long as the bacteria gets enough food. ALL is just too strong here. Also, answer D might contradict itself, because if all other organisms are killed there might be only a limited supply of food, which would not allow for indefinite survival of the bacteria.

[Res Publica]

Because, DlarehAtsok, the stimulus does not support the claim that ALL the oxygen must be removed and ALL other organisms have been killed. It could be that some oxygen remains but is kept out of direct contact with the bacteria, and some other organisms could survive in the area so long as the bacteria gets enough food. ALL is just too strong here. Also, answer D might contradict itself, because if all other organisms are killed there might be only a limited supply of food, which would not allow for indefinite survival of the bacteria.

Is answer choice D a mistaken reversal of A? I chose D, but I want to be sure that is wrong because of the reason I suggest.

stimulus:
KOO + HS --> TI
(Kills other organisms for food and produces Hydrogen Sulfide as waste product, then a dense colony of those bacteria can thrive indefinitely)

Answer A:
KOO + HS --> TI (rephrased)

Answer D:
TI --> HS + KOO

[Malila Robinson]

Hi Res Publica,
I can see how Answer D could be phrased as a MR as you have done here, and it is not necessarily incorrect. But the logical issue that I noticed first was that Answer D used "and" which means that BOTH hydrogen sulfide has removed all oxygen AND all other organisms have been killed. But I don't think the stimulus gets us to the point of saying that both things need to happen. The stimulus simply states that in this case both things did happen, but it doesn't say that it requires both things to happen.
Hope that helps!
-Malila

[Torchia7]

Hi PowerScore Staff!

Why is (B) incorrect?

[Jeremy Press]

Hi Torchia7,

Answer choice B is incorrect because, while we know from the stimulus that (1) hydrogen sulfide removes oxygen, and (2) hydrogen sulfide tends to kill other organisms, we don't know that there is a causal connection between these two processes. It could be that hydrogen sulfide kills the other organisms by directly poisoning them. Or maybe hydrogen sulfide does something else that causes the other organisms to die. We simply can't be sure that the removal of oxygen is the cause of the death of the other organisms.

I hope this helps!

Jeremy

[KG!]

Thanks for all the above explanations! I was just wondering if I am able to eliminate some answer choices by looking at the key phrases. For example
B: this answer choice is super direct. While I could infer this the stimulus only says "the hydrogen sulfide tends to
kill other organisms in the area."
C: where does it say most?
D: the word only helps me to eliminate this answer choice quickly
E: Same problem with B. How do we know "it ensures" the stimulus uses a lot weaker language than this.

A: it's uses the weakest and least direct language which matches the stimulus.

Is this a correct way of going through the answer choices?

[Adam Tyson]

I'm not sure what you mean by "direct" here, KG. The problem with answer B is that it combines two ideas from the stimulus in a way that the stimulus does not support (and so you cannot properly infer it, you can only speculate that it might be true). Answer E is too broad - we only know this is true of certain kinds of bacteria, not any kind that does this.