So I just tried the passage and q, and took a look at what you wrote —
Here are some thoughts —
As always, obviously I can’t read into your mind, so if any of this is not relevant to you, please feel free to ignore it —
First, some general thoughts about the reading process —
1) Per what you wrote, I think the main points you focused on were strong — the next step is to make sure you are reading to understand how the entire passage is structured around those main points (again, you may be doing this already so please feel free to ignore all this if u r) —
To use a movie analogy (as I often do) — your job isn’t just to correctly recognize the main points/scenes of the film, but to try and see as clearly as you can how the director organized the structure of the movie in relation to those key points —
In terms of the passage in question, the author gives the main point of the first paragraph right at the beginning, and then he spends the rest of the paragraph providing support for that point — the main crux of that support has to do with “basalt….contains magnetite….” — I have no idea what basalt and magnetite are, but I know that the purpose of this part is to act as some of the evidence that led to the original main point given.
Those thoughts are what made it so that when I read the stem for Q 18, I knew to look in Paragraph 1 — I also did a quick scan of the other p’s just to make sure magnetite isn’t discussed elsewhere, and I couldn’t find it in the other paragraphs.
Again, if I was just focused on main points it would probably be less likely I would have remembered seeing magnetite in the first paragraph — I think the relating of the support to the main point gave me a better chance of recollecting it.
2) Though I certainly understand the instinct, make sure you are not expecting to find one main point for each paragraph — that’s not how LSAT passages are designed (again, not sure if this is something u are doing but thought I’d mention it).
So now, in terms of the specific problem —
In my opinion, this is a very difficult question — about as difficult an “according to the passage” problem as you are likely to see —
What makes this extreme and unusual is that in order to arrive at the right answer, you have to bring together information from parts of the passage that are very far apart from one another — the vast majority of the time, “according to the passage” q’s will instead require you to bring together or understand information from just one isolated and limited part of the passage.
Because of this, I did not find the right answer very attractive the first time I looked at it, and, personally, needed to rely heavily on my elimination skills before I could figure out what was actually going on.
Fortunately, like many difficult RC q’s, most of the wrong answers were fairly obviously incorrect and easy to eliminate —
With all that said, here’s the play-by-play solution —
Read Q Stem — don’t remember seeing “grains” but remember magnetite from first P — go back to it and read it again carefully — notice “grains of magnetite” and know I’m looking in right place —
Quickly scan other paragraphs to see if there were other mentions of magnetite I missed — don’t see any — return to P1 and read again carefully —
My basic understanding is that these magnetite grains are what in the “basalt,” and these magnetite grains have the same polarity that the earth’s magnetic field had when the grains first came to be. (This sameness is what will be used to support and explain the key findings/theories discussed in the following paragraphs) —
So, with that in mind, I go into the answers —
A) Seems consistent with what I read/understood — but it seems far more like an inference than something actually stated. It also seems to match more what is stated in the final P (about young rocks). Still, I didn’t see a way to eliminate it and I left it.
B) Most of this answer sounds great, but the “most but not all” catches my eye. Still, close enough to leave for closer inspection.
C) I don’t remember this being discussed, and can’t imagine why it would have been — whether they could be found in other types of rock or not would not impact the author’s point — I do a quick scan and don’t see anything related to this and cut it.
D) Similar to C — I don’t remember this being discussed and can’t imagine why it would be — I do another quick scan and eliminate it.
E) Similar to C and D — don’t need to read passage again because I just checked for size info and know that it’s not there.
Okay, so I hate that a right answer didn’t jump out at me, but I am down to just two — I look them over again carefully, starting w/the one I was most suspicious of — (B) —
(B) claims something very specific — “most but not all” and I don’t remember seeing this anywhere. On closer inspection, (B) is, in addition to relating to the part, “in magma…grains of magnetite….align themselves with…,” also seems to be connected in a way to the statement — “…some basalt…same polarity…” but that would be a false connection to make, and, regardless, there is no match for “most but not all.” (B) is not something true according to the passage —
I move on to (A) hoping I can see why it is correct —
So, looking back over the first paragraph, I can see why (A) is fairly easily inferrable — we are told in the first P that the magnetite grains in basalt rock align with polarity of the earth when the basalt rock is formed, and it makes sense, thus, that the youngest besalt would match the current polarity of the earth.
But, there’s a slight itch at the back of my head — how do you define youngest?
It’s a small thing, but again, the q is asking for what the passage actually states, not what I can infer from it, and the first paragraph doesn’t give us a definition of “youngest” that tells us for sure that the rocks in this category have the same magnetic polarity as the earth currently does.
In addition, I clearly remember reading about “youngest” in the final paragraph — and that’s where I get the final key piece of evidence — “youngest rocks all have normal polarity.” — the rocks in question are basalt(!), and so this information coupled with what we’ve been told of magnetite in the first P allows me to confirm (A).
Whew! Hundreds of words to describe what was probably less than a minute of thought — sorry for the length and I hope that made sense — I’m too lazy to edit it all down now — anyway, if you have any follow-up q’s, just let me know —