Reading comp PrepTest 154 · Section 3 · Question 18

Passage

 For nearly a century after the discovery in the 1880s that a bacterium, Vibrio cholerae , causes cholera, scientists believed Remaining source text redacted.
Passage walkthrough
Passage SummaryTopic: Science

Paragraph 1
  • Paragraph note
    • A common scientific belief is discussed, and a question it leaves open is raised
  • Views, minor Meta-Structures, and the author's attitude
    • Common belief - Cholera travels via human hosts (waste into food and water supplies)
    • Question - How do spontaneous outbreaks in areas cholera was eliminated happen?
Paragraph 2.1 (Lines 12-25)
  • Paragraph note
    • A new belief is brought up and skepticism is discussed
  • Views, minor Meta-Structures, and the author's attitude
    • Rita Colwell (1970s) - Claimed to have found cholera in seawater and it can go undetected by common culture tests
    • Skepticism - "No" biologist thought it could live outside of humans, and there were no outbreaks since 1911
Paragraph 2.2 (Lines 25-39)
  • Paragraph note
    • Colwell's hypothesis is put to the test
  • Views, minor Meta-Structures, and the author's attitude
    • Colwell used a new test (antibodies/UV) and found cholera bacteria in bayous that traditional tests missed
Paragraph 3
  • Paragraph note
    • Further studies backing up/expanding on Colwell's hypothesis, and a future course of inquiry
  • Views, minor Meta-Structures, and the author's attitude
    • Tests show bacteria go into sporelike state that can't be detected using traditional tests
    • That state is more survivable
    • Question - What gets them out of sporelike state? Potential answer - Sea-surface temp spikes (e.g., Bay of Bengal)
Main Point:
There is evidence suggesting that Rita Colwell's hypothesis about "viable but nonculturable" cholera bacteria surviving in the ocean and in a sporelike state is correct, as it explains seemingly spontaneous outbreaks of the disease in areas where it has been eradicated.

Key Lines:
Lines 3-6 - Traditional scientific theory is discussed
Lines 9-11 - A question left open by this theory
Lines 12-14 - A new scientist/theory is introduced
Lines 21-24 - More on that theory
Lines 25-30 - The new theory is tested
Lines 40-42 - The new theory is expanded
Lines 49-51 - A question is posed for the new theory
Lines 51-54 - An answer is put forward

Meta-Structure:
Old Theory/New Theory - The old theory concerning the spread of cholera is shown to leave open a question that a new theory answers.

Question/Answer - Two questions are posed. The first (Lines 9-11) is broad and leads to the main point - Colwell's new theory. The second (Lines 49-50) is limited and leads to a hypothesis to be tested under Colwell's theory.

Last Thoughts:
Normally, the Author is a bit more on board with a new theory being presented. Here, there's a mix. She states that Colwell's studies "revealed" some things about V. cholerae (Line 40), but also poses Colwell's water theory as being something that isn't 100% certain ("If, as Colwell believes" in Line 54).

So we need to be careful in selecting answers that don't overshoot the Author's feelings towards Colwell's theory and pick an answer that reflects a certainty that doesn't exist.

Also, note that we split Paragraph 2 up. It was pretty long, and there was a natural breaking point between where Colwell raised her claim and people expressed skepticism, and the specific situation that allowed her to discover evidence for her hypothesis.

Question prompt

Which one of the Remaining source text redacted.
Why the credited answer is right

Credited answer: A

The notes below walk through why it fits the stem and how to eliminate the rest.

Question Type

Science

Answer choices

  1. A
    V. cholerae bacteria in Remaining source text redacted.
    Why choice A matches the stem
    Correct. Question Type:
    Must Be True

    Strategy Overview:
    The question stem gives us no guidance, so we're going to have to head straight to the answers and use our notes/the passage to find the correct one

    Answer Anticipation/Relevant Lines:
    Without any guidance in the question stem, we can only reiterate the overall point of the passage and then head straight to the answers, focusing on those that line up with that viewpoint. Here, we said the main point was:

    There is evidence suggesting that Rita Colwell's hypothesis about ""viable but nonculturable"" cholera bacteria surviving in the ocean and in a sporelike state is correct, as it explains seemingly spontaneous outbreaks of the disease in areas where it has been eradicated.

    Let's use that and our overall understanding of the details to find the correct answer.

    Answer Explanation:
    (Lines 24-25; Lines 52-59) The traditional culture methods are introduced in Lines 24-25, and we know that they require non-dormant bacteria to detect. The last paragraph talks about seasonal sea-surface temperature peaks in the Bay of Bengal and how they ""correlate closely"" with outbreaks of cholera. So during those peaks, there must be active bacteria, and thus it could be detected by the traditional methods. This answer is therefore correct.

    Key Takeaway:
    This was a tough question, and the answer requires putting together a few different pieces that aren't straightforward. Use the strength of the answers and the language in the passage to find one where both the content and the force match up.
  2. B
    When the salinity of Remaining source text redacted.
    Why choice B is not credited
    Incorrect. (Lines 55-59) The Bay of Bengal is discussed starting in Line 52. There, the Author states that it's ""possible"" that ""changes in...salinity"" might lead to cholera outbreaks. This answer therefore has three issues. First, the passage says it's ""possible,"" not likely as this answer choice claims. Second, a change in salinity is only one of two possible changes noted. Third, the passage talks about a change in salinity correlated with outbreaks—that could be an increase in salinity as easily as a decrease.
  3. C
    Although V. cholerae can Remaining source text redacted.
    Why choice C is not credited
    Incorrect. (Lines 12-18) Colwell found V. cholerae in the Chesapeake Bay despite there being ""no cholera outbreaks"" anywhere nearby. Therefore, it seems to have spread without a human host, contradicting this answer.
  4. D
    Bacteria that are taken Remaining source text redacted.
    Why choice D is not credited
    Incorrect. (Lines 34-39) The traditional test found only 7 cases where the new test found 51 when looking at bayou water. That doesn't speak directly to seawater. However, it does suggest that the traditional test isn't good at detecting cholera in water, and we know that it can detect it when it's not dormant—i.e., when it's causing an infection. As such, it's reasonable to infer that the traditional test is better at detecting cholera from human samples than from seawater, contradicting this answer.
  5. E
    Antibodies are less likely Remaining source text redacted.
    Why choice E is not credited
    Incorrect. (Lines 32-47) Colwell's test—which uses antibodies bonding to the cell membrane—was able to detect V. cholerae when the traditional test wasn't, and she theorized this was because the bacteria was in a dormant state. If anything, that suggests that her test works well on dormant bacteria. While that doesn't contradict this answer (since it's a comparative one), it's more in line with an argument against it than for it.

What this tests

Question analytics

Based on historical answer selection rates for this question.

Answer choice distribution

  1. A Credited 47%
  2. B 15%
  3. C 20%
  4. D 7%
  5. E 11%

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