#24 - Specific Reference, Must Be True, Purpose/Function

[deck1134]

Hi PowerScore,

What would a prephrase for this question be? I got it right but am not sure why (always a bad sign).It certainly isn't A or C, but I was stuck here for a while.

[Sky Brooks]

Hi Deck,

These "must be true"/"function" questions can be very tricky to prephrase. In the question stem they ask, "What is the specific role played by the phrase, 'all other atmospheric gases' in line 46?" After reading that question stem, I will immediately return to that phrase in line 46. I then reread that line and see how it connects to anything meaningful in the passage.

In this passage, the author states that oxygen and all other atmospheric gases are excluded from cells containing rubisco. There is a sentence shortly thereafter that connects these types of cells with the process that carbon dioxide undergoes, a series of reactions to form an intermediary, nongas molecule named C-4.

There is a lot to digest in this passage, but after re-reading from the specific point that the question stem references (which I nearly always do on these types of questions), I connected that phrase with the key terms "carbon dioxide reaction" and "C-4". Answer D was the only answer that directly referenced the transformation that carbon dioxide undergoes which ultimately promotes the proliferation of C-4 plants. Because of that, my prephrase made D stand out immediately as a strong contender, although I did disprove other contenders before settling on D.

It's always good to prephrase, but when dealing with complicated questions that reference a specific line or phrase in the passage, it is generally best to revisit that specific line and thoroughly understand the role it plays in the passage. Often these types of questions are just harder to solve using prephrasing.

Hope that helps,
Sky

[amys45]

Hi there,

I have a question about this one. I see from your explanation how "D" is the correct answer. However, when I was originally taking this PT, I chose answer choice "B" because in the paragraph above (paragraph 2) the author says that the presence of other common atmospheric conditions can cause the concentration of oxygen relative to carbon to interfere with the photosynthetic reaction. I thought that this was the point of this question, and thus chose "B".

Could you help me understand why this is incorrect?

Thank you so much

[Adam Tyson]

There are two good reasons that I see for rejecting answer B, amys45, and your question actually captures one of them. Answer B refers to "the claim advanced earlier in the paragraph." That means that you would have to find a claim about other gasses in the third paragraph in order to select this answer. As you pointed out, the evidence you found was in the second paragraph, not the third, so answer B does cannot be referring to that evidence.

Also, the evidence from the second paragraph was too vague, because it referred only to "many common atmospheric conditions" without specifically including any other gasses. Are there any gasses besides oxygen that interfere with photosynthesis? We can't be sure based on that broad statement about atmospheric conditions. Those could be referring to temperature, moisture, radiation, particulate matter, etc.

[amys45]

Hi Adam, thank you so much! That makes a lot of sense and is a great reminder to read the answer choices very carefully!

[bella243]

There are two good reasons that I see for rejecting answer B, amys45, and your question actually captures one of them. Answer B refers to "the claim advanced earlier in the paragraph." That means that you would have to find a claim about other gasses in the third paragraph in order to select this answer. As you pointed out, the evidence you found was in the second paragraph, not the third, so answer B does cannot be referring to that evidence.

Also, the evidence from the second paragraph was too vague, because it referred only to "many common atmospheric conditions" without specifically including any other gasses. Are there any gasses besides oxygen that interfere with photosynthesis? We can't be sure based on that broad statement about atmospheric conditions. Those could be referring to temperature, moisture, radiation, particulate matter, etc.

So when it comes to specificities purpose questions, is it best to focus on the paragraph where the reference is stated? In other words, in this case, the reference was in paragraph 3, so do I need to re-read para 3 to prephrase, and not paragraph 2?

[evelineliu]

Hi Bella,

I read some of the context before and after the line reference as well. Typically, if I get an explicit line reference, I'll also read five lines above and five lines below. Lines 50-54 tell you that "carbon dioxide, which cannot enter these cells as a gas, first undergoes a series fo reactions to form an intermediary, congas molecule named C-4." The author points out that all atmospheric gases are excluded from the bundle sheath cells because doing so explains the necessity of the chemical transformation of CO2 into C-4.

Best,
Eveline