Whenever you are given a specific line to reference, make sure to read a few lines above and below it as well. We know that at the end of the second paragraph, we discuss the reversal phenomenon and what may trigger it: "when something disturbs the heat circulation pattern of the outer core fluid, and with it the magnetic field."
The next paragraph starts by introducing several explanations for this phenomenon, on of which is the "heat-transfer hypothesis," which states that the "triggering process is intimately related to the way the outer core vents its heat into the mantle." The passage goes on to give the example references in the question about blobs of different temperatures in the Earth's outer core.
SO what's the purpose of this? It's to give ONE EXPLANATION as to why the heat-circulation pattern is disturbed within the outer core, what we were discussing right above the actual referenced lines. This is clearly found in answer choice (A).
Answer choice (B) is incorrect because the blurb example is not to provide proof for the proposal that ventilation of heat from the outer core into the mantle triggers polarity reversal. We are told that the reversal phenomenon, i.e. that the polarity field is reversing, may be triggered when something disturbs the heat circulation pattern and the examples given beneath that are to attempt to explain the disturbance rather than the reversal phenomenon.
Answer choice (C) is incorrect because the blob example is given to show one way "that the heat-transfer hypothesis is intimately related to the way the outer core vents its heat into the mantle."
Again, answer choice (D) is incorrect because the example is given to help show one way "that the heat-transfer hypothesis is intimately related to the way the outer core vents its heat into the mantle."
Answer choice (E) is incorrect because the blurb example in the referenced lines has nothing to do with the Earth's interior producing the magnetic field.
It's important to note the structure of the passage, i.e. how the reasoning moves a long. Don't get various topics touched upon in the passage mixed up and rearranged. It's important to understand exactly how the author is making their point so that you can pinpoint the purpose of each statement. A great way to do this is to write the main point of each paragraph (in shorthand) in the margins as you read. This will be a great roadmap to look back on and see exactly how the author structures their point.
Hope that helps! Please let us know if you have any other questions.
pmornelasperez@ucdavis.eduSeptember 6, 2020
Hi, this explanation doesn't really make sense. Could you please reword
