This question popped up on our
Ask Me Anything About SC thread. Reposting it here just in case it helps somebody else:
Mallard wrote:
Hi Charles,
I faced a question in a mock that I was unable to solve. Can you please provide an explanation for this?
The discovery that Earth's inner core rotates independently of and more quickly than Earth's outer layers is responsible for advancing studies of the flow of heat from the inner through the outer planet and of the formation and periodic reversal in direction of Earth's magnetic field.
1. core rotates independently of and more quickly than Earth's outer layers is responsible for advancing studies of the flow of heat from the inner through the outer planet and of the formation and periodic reversal in direction of Earth's magnetic field
2. core rotates independently of and more quickly than Earth's outer layers is responsible for advancing studies of how heat from the inner core flows through the outer planet, and the formation and periodic reversal in direction of Earth's magnetic field
3. core rotates independently and more quickly than Earth's outer layers are responsible for advancing studies of how heat from the inner core flows through the outer planet, and how Earth's magnetic field forms and the periodic reversal of its direction
4. core, rotating independently and more quickly than Earth's outer layers, are responsible for advancing studies of the flow of heat from the inner through the outer planet, and the formation and periodic reversal in direction of Earth's magnetic field
5. core, rotating independently of and more quickly than Earth's outer layers, is responsible for advancing studies of the flow of heat from the inner through the outer planet and of how Earth's magnetic field forms and the periodic reversal of its direction
Correct answer is [A], and i can't understand why?
SC is less about why the correct answer is right than why the incorrect options are wrong. The key here, as Shrey9 notes below, is the parallel construction demanded by the multiple uses of "and," and how this construction shapes the meaning of the sentence.
First, take a look at (A), stripped down:
"The discovery [long modifier] is responsible for advancing studies of the flow of heat from the inner through the outer planet and of the formation and periodic reversal in direction of Earth's magnetic field."
Because "of the formation" ("preposition + noun") comes right after "and" we want a similar construction to precede it. In this case, we find "of the flow of heat." Now we want to ask ourselves if these two elements are logically parallel. And it makes perfect sense that the discovery is responsible for advancing studies of two things: (1) of the flow of heat and (2) of the formation and reversal of the earth's magnetic field. So keep (A).
Now compare that with all the other options. (B), (C), and (D) all lack the "of" before "formation." Is the preposition absolutely mandatory in a grammatical sense? No. But because the sentence is so complicated, it becomes very very difficult to see that the discovery is responsible for advancing studies of two separate elements if we don't include "of" before both of them. This confusion is enough to get rid of these options, but if you're skeptical, let's find a more concrete error in each:
Quote:
(B) The discovery that Earth's inner core rotates independently of and more quickly than Earth's outer layers is responsible for advancing studies of how heat from the inner core flows through the outer planet, and the formation and periodic reversal in direction of Earth's magnetic field
Here, the "comma + and" creates the expectation that we're going to be treated to new information, potentially unrelated to what we've seen thus far. Put another way, it sounds as though "the discovery" is responsible only for advancing studies of how heat flows, and then there's this new clause about "the formation." But there's no verb to go with "formation!"
When we look back at the sentence, it appears that the discovery is responsible for "advancing studies" and for "the formation" itself. My physics is a little rusty, but I'm confident that a discovery can't be responsible for the formation of a magnetic field. That's illogical, so get rid of (B).
Both (C) and (D) have the same subject-verb agreement error: "
The discovery... are responsible," so those are out.
And here's (E):
Quote:
The discovery that Earth's inner core, rotating independently of and more quickly than Earth's outer layers, is responsible for advancing studies of the flow of heat from the inner through the outer planet and of how Earth's magnetic field forms and the periodic reversal of its direction.
First, it sounds like the "earth's inner core" is itself responsible for advancing studies. Worse, there's no main verb here to go with the subject "the discovery." So this is illogical and ungrammatical. (E) is out, and (A) is our winner.
I hope that helps!
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