#4 - Concept Reference, Must Be True

[Administrator]

Complete Question Explanation

The correct answer choice is (B).

Answer choice (A):

Answer choice (B): This is the correct answer choice.

Answer choice (C):

Answer choice (D):

Answer choice (E):

This explanation is still in progress. Please post any questions below!

[coolbeans747]

Where in the passage is the evidence for this answer?

[Malila Robinson]

Hi coolbeans747,
In the first paragraph, the second sentence states: "Geological evidence shows that periodically the field's polarity reverses, and that these reversals have been taking place at an increasing rate." This sentence provides support for Answer B.
Hope that helps,
-Malila

[RottenPJ]

I do not see how B can be most supported here.

A states that most geophysicists must accept the notion that the polarity exists in two distinct states. It says in the passage that this is a "fundamental tenet of geophysics." How is this not supported?

E also seems supported. "This redistribution increases the rotational acceleration of the mantle, causing friction and turbulence near the outer core-mantle boundary and initiating a reversal .... "

I do not see how B is supported because it says "it has been occurring at an increasing rate. This need not be a consistent straight increasing rate since the beginning of time, it could be more recent. Therefore, generalizing about the past vs the past I do not see how this is supported.

[Jeff Wren]

Hi RottenPJ,

Regarding Answer B, the terms "recent" and "distant" (while admittedly somewhat vague) should be understood in context to be relative to each other rather than referring to a precise period. In other words, the word "recent" here means recent in geological terms, not as we'd use it in other contexts. For example, we know from the passage that just the process of switching polarity itself "typically spans a few thousands years' (lines 12-13).

The statement in the passage that "these reversals have been taking place at an increasing rate" (lines 8-9) does mean that the reversals are happening more frequently in more recent time periods than in less recent time periods. Otherwise, the rate would not be increasing. Answer B is stating a general trend rather than comparing two specific time periods.

As for Answer A, it looks like you missed a critical part of the answer (in fact, the part that makes the answer wrong). Answer A states "most, but not all, geophysicists agree..." (my emphasis). If it is a "fundamental tenet of geophysics" (line 1) as stated in the passage, one might expect all of them to agree on this idea. There certainly isn't any mention of any disagreement on this issue in the passage. It would be like claiming, "Most, but not all, mathematicians agree that 2+2=4." That's something that we'd probably expect all mathematicians to agree on.

As for Answer E, this idea is discussed in the passage as part of the "more controversial alternative proposal" (line 39), called the "asteroid-impact hypothesis" (line 40). The rest of this paragraph describes what this hypothesis argues, including the part about friction near the outer core causing the reversal of the magnetic field.

The problem, though, is that the author of the passage finds the asteroid-impact hypothesis "less convincing" (line 60) than the "heat transfer hypothesis." It's critical in reading comp passages to correctly track different viewpoints/theories because not everything that appears in a passage is the author's view. A viewpoint or theory that the author discredits or questions in the passage would not be something that is supported by the passage.