PT19.S2.Q04 - scientists analyzing air bubbles

tanes256

I had this one down to C and D and ultimately went with C. I saw C an an alternate explanation but would C have been eliminated because the increase was not specifically mentioned a well as the FM? Do both A and B both have to be specifically mentioned and not implied or assumed? Also, I get that C is incorrect because C-> A&B (Other M -> FM & Increase isn't possible due to no assumption in the stimulus that FM caused the increase but is instead the conclusion, so FM->Increase (A->B) was never a possibility. I ultimately eliminated D because I interpreted the AC as saying there was no increase in the algae population because there was no increase in the amount of shells left behind. I took that as meaning constant but didn't go further and see that it meant that we should see more shells if there was an increase, thus weakening the argument. Hopefully this all makes sense for you guys.
https://7sage.com/lsat_explanations/lsat-19-section-2-question-04/

Sami

So it was a bit confusing to understand what you meant exactly. So I am sorry if I end up not answering important parts of your questions. I hope this still helps you.

Our stimulus starts out with a phenomena that needs to be explained: We have a lot of Ferrous Material and a few amount of CO2.
Our conclusion in the stimulus is: Ferrous material had promoted an increase in Algae population such as Diatom.
This is supported by the premise that: Algae absorb CO2 from the atmosphere.

Explanation: Our conclusion is trying to give an explanation of why we could have a lot of Ferrous material but not a lot of CO2 in this ice in Antarctica. An explanation/hypothesis is put forward that this may be due to Ferrous material promoting Algae population which absorbs CO2 leading to the phenomena of high ferrous material and low CO2.

* If you note the conclusion is causal in nature as well: Ferrous material was the cause of an increase in Algae population/Diatom which caused the decrease in CO2.

When I read this stimulus, since my job was to weaken the argument and I saw a causal conclusion I was on the look to weaken that causal relationship. There are few ways to weaken a causal conclusion: cause without effect, effect without cause, Alternate cause, and the relationship can be reversed. I have listed below answers that would have worked in accordance with these methods:
1. Cause without effect (An instance of ferrous material not promoting an increase in Algae/Diatom population or instance of Algae increasing but not a decrease in CO2)
2. Effect without cause (An instance of Algae/Diatom without Ferrous material (though this wouldn't work as well here) l, or an instance of no Algae/Diatom but a decrease in CO2 in atmosphere.
3. Alternate cause: An example of something else that could have lead to the decrease in CO2 or an increase in Algae.
4. Cause and Effect are reversed: I just didn't see how this was plausible for this example; but in other cause and effect stimulus this could be a possibility.

So lets dissect our answer choices:

A) Diatoms have remained unchanged: Our stimulus has nothing to do with Diatoms not changing/changing. Lets say the Diatoms have remained unchanged; doesn't that just mean they are consuming CO2? This is in line with our conclusion that diatoms are absorbing CO2 and therefore do not weaken our relationship with Algae and Ferrous material and algae and CO2. This answer choice really does not affect the argument at all.

Ferrous material could promote the growth of Algae: This is confirming our causal stimulus and is actually strengthening our conclusion instead of weakening it. This is more evidence of how our conclusion is right. So lets eliminate this.

C) That dust found in Air had other minerals as well: so it had other stuff in around it. Does it affect our relationship of Ferrous material with algae? Not at all. We have no idea. So lets eliminate it.

D) This answer choice states that evidence indicates there was no rate of increase in the shells that diatoms leave when they die. This directly affects our relationship that that we had an increase in Ferrous material and decrease in Co2 but no corresponding increase in Algae/Diatom as there were no increase in their shells which would indicate that their population had increased. Because this affects our relationship of Algae/Diatom and Co2 and Ferrous material in a negative manner this weakens our conclusion. It is not possible to have an Ferrous material promote growth of Algae but the rate of death of Algae to remain the same.

E) Algae do not appear to be harmed by Ferrous Material: Well this again does not weaken our relationship between Ferrous Material and Algae. In fact, it is completely in agreement with our conclusion. If Ferrous material did promote Algae which absorbed CO2 then Algae should not have been harmed by Ferrous Material.

* I hope this helped you. Let me know if you have any further questions. : )

tanes256

@Sami thx for the thorough response! I got exactly what I needed. My only remaining question is regarding C. If it were discussing a causal relationship like something else caused both A and B, does the AC have to specifically mention both A and B? Or, can it be implied from the wording that something else is causing both if only one is specifically mentioned? Would that be a good reason to eliminate if both aren't specifically mentioned?

Sami

@tanes256 said:
If it were discussing a causal relationship like something else caused both A and B, does the AC have to specifically mention both A and B

So in short No, it is perfectly fine for an answer choice to be weakened by finding an alternate cause for only one. So, yes, don't eliminate something only because one is mentioned.

But I think what you might be asking me here is if answer choice "C" is an alternate cause for one of them. The answer is "No". Answer choice "C" is just talking about other materials being present. It does not talk about any relationship that these minerals have with Ferrous materials, CO2, or even Algae. Answer choice "C" is just irrelevant.

I hope this helped. Let me know : )

tanes256

@Sami ok thx! The first portion of your response was what I was asking but the second portion was informative as well because I did take it as being an alternative cause. I am determined to conquer this darn question type!

Sami

@tanes256 said:
I am determined to conquer this darn question type!

I am sure you will

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