Q7

[kjg56]

I know that the relevant information for answering this question is found in lines 41-47 and I see how answer D is supported in those lines.

I had a hard time eliminating B. Is the problem with B "...caught in the shifted sediments." I assumed (you know what happens when you assume...) that "caught in the shifted sediments" was equivalent to "...looking for sediments that show evidence of having shifted [in the trenches]." Was this my downfall?

Thank you!

Kate

[ohthatpatrick]

I would say your ‘downfall’ / important takeaway for this and most other RC questions is to get better at finding the keywords in the question stem and then finding them in the passage. If you’re looking in the 1st paragraph for support for this answer, then you’re doing it wrong.

What would you say are the keywords in this question stem?

It seems like you mainly looked for ‘radiocarbon dating’ / ‘earthquakes’, when the REAL important keyword is unreliable.

In 47-48 we find “causing many radiocarbon datings of events during this period to be of little value.”

Our answer HAS to be tied to that line reference, because that's the only time the passage talks about radiocarbon being unreliable.

The "shifted sediments" in (B) certainly IS referring to what you were talking about: scientists digging trenches, looking for shifted sediments, and then measuring wood or other organic material for its date.

There's just nothing in the passage there about it being unreliable!

== other answers ==

(A) Who said that a bunch of different types of matter REQUIRE analysis?

(C) "not always" is super weak, and this wouldn't make radiocarbon dating unreliable, it would make it impossible for that site.

(D) lines 45-48

(E) "upper atmostphere"?

[Fazzvm56]

I ended up picking the correct answer, but I didn't necessarily eliminate (E) comfortably.

(E) - "the possibility of that radiation has not always struck the upper atmosphere".

Lines 41 - 45 state "Radiocarbon dating is accurate only to within plus or minus 40 years, because the amount of carbon 14 isotope varies naturally in the environment depending on the intensity of the radiation striking Earth's upper atmosphere."

So I felt that answer (E) was kind of relevant, but I ended up not picking it because I felt that if it wasn't always striking Earth's upper atmosphere, it would make it more reliable instead of less.

[ohthatpatrick]

Thanks for the follow-up.

I'm surprised I didn't register that the passage had ever mentioned 'upper atmosphere', given that my (non-helpful) way of eliminating (E) was "upper atmosphere?"

This is really a symptom of what I was talking about in my original post --- because I start by finding the window of text being advertised by the keywords in the question stem, I only end up seeing that window of text before I look at the answer choices.

Searching for some synonym for "unreliable", I found "of little value" in the following line and thus knew I had my answer.

I would just say that (E) and lines 41-45 are speaking about two different things.

lines 41-45 are talking about the INTENSITY of radiation hitting the upper atmosphere (a comparative sense of MORE vs. LESS).

(E) is saying, "radiocarbon dating might be unreliable because it's possible that at some point in the past, radiation DID NOT STRIKE the upper atmosphere."

The issue the passage was discussing was the RELATIVE level of radiation, not the ABSOLUTE quality of whether or not radiation hit it.

Hope this helps.