Yes, jabhatta2, it's the latter. But, as AnthonyRitz explained, it's irrelevant. I mean, how would you react if you found a text that appears to have been written in 1910, that describes in detail the events of World War II? The text itself doesn't say that these events took place in 1939-1945, but we all know that they did. Wouldn't you question how a 1910 text could possibly describe events that hadn't yet happened? Does it really matter whether the text itself mentions the years 1939-1945?

Take another look at the beginning of the argument:
What was your reaction, when you took a pause at that point? Did you not infer that the text must have been written no earlier than the year 1165? If not, that was your first mistake.
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Hi avigutman AnthonyRitz - thank you so much for your inputs.

What both of you said in the posts just above make sense. - the book was definitely written AFTER 1165 (that cannot be disputable) - I did not make that inference. I understand the logic for this now

The only thing questionable is : was the text written PRIOR to 1167

While we are only left with (c) so we have to pick (c) -- however, would you agree on these inputs on (C) ?

-- Traditionally most GMAT assumptions are necessary assumptions. (C) seems to go over-board

Here is why :

(C) is is suggesting two things

(i) mom / dad / brother / sisters /grandmom / grand-dad / grand-mom / great grand mom / great grand-father / children / wives / cousins = EVERYONE IS ALL listed accurately.
(ii) LIVING / Deceased STATUS of EACH ONE is listed accurately as well.

(C) is suggesting both the above bullet points.

However, I think only DAD and the living /deceased status of DAD specifically is necessary for this argument.

If mom / brother / sister /grandmom .... is listed incorrectly and THE LIVING STATUS of mom / brother / sister / grandmom is listed in-accurately as well --- it doesnt hurt the argument.

Thoughts ?

If you conclude that the text was written no later than 1167, and your only evidence is a diagram, then, yeah, your argument requires that the diagram be accurate.
It's true that we only need one little part of the diagram to be accurate, jabhatta2, but the answer choices aren't granular enough so as to question the accuracy of each part of the diagram separately.
Negation test: if we find out that the diagram does NOT accurately represent the composition of Sviatov's family at the time Sviatovin was written, then the entire logic behind the conclusion (that the text was written no later than 1167) crumbles.
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Yeah I'm not convinced that this is the typical necessary assumption question, but even if it was, imagine negating C:



Then I'd say the family tree showing the father alive gives no reason whatsoever to assume that Sviatov's father was actually alive when the book was written. And therefore the conclusion is, if not wrong, at least without any basis in the argument. I'd consider that a good enough basis to pick this answer.
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