Archeologists have recently unearthed a 250-page bible

D is also my choice. here is the reasoning

Conclusion: The book was written around 1759
Premise: The book mentions an earthquake that killed many people in Safed in 1759.

The answer choices should bring the above two closer. Lets have a look at the options
A: Irrelevant
B:Also an irrelevant detail
C: The mention of time is again irrelevant and not very helpful in solvingif the book was written around 1759
D: If there was only one earthquake in Safed during 18th centuary, it would firm up the conclusion that book was written around that time, an option that can be considered.
E: Not very pertinent to the discussion here.

I will go for D too.

Why?
All other four are irrelevant. Only D talks about the earthquake and its time.

Let me give a crazy attempt: B

Archeologists have recently unearthed a 250-page bible commentary in Safed. The document is undated but contains clues to when it was written. The first 130 pages are written by one hand, while the rest is written in a distinctively different hand. Since a letter in the handwriting identified as that of the second writer reports on an earthquake that killed many people in Safed in 1759, the commentary was probably produced around that time.

Fist of all I would like to focus your attention on following things:

1. "...the second writer reports on an earthquake that killed many people in Safed in 1759." I have no doubt that the second writer reported the date - 1759.

2. "...the commentary was probably produced around that time." What does the author of the argument mean? Does he/she mean the same year? The second author could write the commentary 50 years after the earthquake.

Which of the following, if true, most strongly supports the hypothesis that the commentary was produced around 1759?

a) Other than this commentary, there are no known samples of the handwriting of the first writer. - it is very close. For example, if there were known samples of the handwriting of the first writer dated 1800, it would destroy the conclusion.

b) According to the account by the second writer, the earthquake caused the collapse of over fifty structures. - What could the second writer count? Could the second author count collapsed structures 50 years after the earthquake? The second author saw this collapsed structures that would be rebuilt in the next years. Does the reasoning make sense?

c) A commentary like the one unearthed would usually take between three to nine months to write. - The second author could write the commentary 50 years after the earthquake.

d) There was only one earthquake in Safed in the 18th century. - The second author pointed 1759.

e) It is highly unusual for such a document to be written by more than one hand. - no comments

I think B wrong not b/c B is irrelevant, B does say about the evidence-the earthquake- that argument points out to go to a hypothis. But, B does not as strongly sport as D b/c B does not mention the time happening.

the OA is D. I thought it was t tricky question