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#7 - Specific Reference, Must Be True

• PowerScore Staff
• Posts: 8317
• Joined: Feb 02, 2011
#81492
Complete Question Explanation

The correct answer choice is (E).

This explanation is still in progress. Please post any questions below!
biskam
• Posts: 124
• Joined: Aug 18, 2017
#40685
Is A incorrect because while the passage said PD pump had all these qualities, we can't assume that these qualities are in comparison to the centrifugal pump?

Like Cindy is good at soccer. Bob likes to eat. It would be incorrect to then say that Cindy is better than Bob at soccer.

Along this same vein if my understanding of this flaw is correct, how can we say that E is then correct? We know via line 38 that the PD pump is exposed to a lot of crude. But I feel like the rest of the passage tells us nothing about how much of crude or how little the centrifugal pump experiences. As in, there's no comparison.

So how is E correct? How can we make the comparison here but not in A?
nicholaspavic
• PowerScore Staff
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• Joined: Jun 12, 2017
#41637
Hi biskam,

I don't know if you have carefully read this passage because (A) is not really supported.

First of all, the author characterized the PD pump as "promising" but not "more promising." In other words, the comparative language that you read into the passage is not there. We know from the passage that the PD pump's material is also "expensive" (line 38) but we don't know anything about its relation to the cost of the centrifugal or the PD pumps overall cost, for that matter. We know that the centifugal pump requires "less maintenance" (line 43) in waste disposal plants but we don't know about its crude maintenance requirements and we certainly don't know anything about its comparative maintenance to the PD pump. In other words, there are no reasonable inferences from the passage that support (A) as a choice. Which makes me wonder if you are really slowing down in your reading to absorb the materials and critically think about them.

Good luck in your test preparation and please consider slowing down your reading to make sure that you are deeply comprehending the passages before jumping into the questions.
qiranz
• Posts: 4
• Joined: Jul 23, 2021
#89024
I have a question about C. I am having difficulty eliminate C because the second sentence of paragraph two states that PD pump "consists of a single or twin screw pushing the fluid from one end of the pump". In the next sentence, the author discuss centrifugal pump, which is the other pump being redesigned. It "has a rotating impeller that sucks fluid in at one end and forces fluid out at the other". I wonder if I can assume that PD pump and centrifugal pump use different mechanisms to push the fluid from one end of the pump to the other. PD pump uses "a single or twin screw", while centrifugal pump uses "a rotating impeller".

I applied the same logic to E, I understand that PD pump is expensive because of its consistent of "a single or twin screw ...., brings crude into close contact with most prats of the pump." But the author doesn't say the centrifugal pump does not brings crude into close contact with most parts of the pump, why can we assume centrifugal pump is otherwise?

I tried to argue backwardly to support E: it is PD pump's "bringing crude into close contact with most parts of the pump" makes it expensive. If centrifugal pump doesn't bring crude into close contact with most parts of the pump, it may not be as expensive as PD pump. In this line of reasoning, I can conclude that E is correct.

However, if E is correct because of what I mentioned above, why C is not as well supported as E, since "involves the use of a single or twin screw that sucks fluid in at one end of the pump is how PD pump works, and it "brings crude into close contact with most parts ..."?

Beatrice Brown
• PowerScore Staff
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• Joined: Jun 30, 2021
#89082
Hi Qiranz! Thanks for your question

Answer choice (C) actually mixes up the characteristics of the positive-displacement and centrifugal pumps! According to the passage, the positive-displacement pump's design pushes fluid and the centrifugal pump's design sucks in fluid. However, answer choice (C) states that the positive-displacement pump sucks in fluid, which is the opposite of what the passage states.

We can infer answer choice (E) is true from the passage because the passage tells us that the positive-displacement pump's design puts crude into contact with most parts of the pump, and that the centrifugal pump has a different design. Since the centrifugal pump has a different design and the passage states that the design of the positive-displacement pump is what puts crude into contact with most parts of the pump, we can infer that one difference between the two pumps is that the positive-displacement pump comes into contact with crude but the centrifugal pump does not.

I hope this helps, and let me know if you have any other questions!
qiranz
• Posts: 4
• Joined: Jul 23, 2021
#89101
Thank you! I thought push and suck is the same in the context because they all mean fluid goes into the pump from one direction. My mistake! Thank you very much for clarifying that!

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