How will the right answer fit in terms of support and conclusion?

Only the right answer will be a conclusion supported by the passage.

Highlight the main conclusion in the passage, if there is one:

There’s no conclusion in the passage. The right answer will be the conclusion.

[BACKGROUND]. But [SUPPORT], and [SUPPORT].

Map the wording of the answers to the wording of the passage:

(A) The more detailed and complete the evidence…

There’s no mention of evidence being “more” or less “detailed and complete”. That conclusion isn’t supported by the passage.

(B) The more general…, the more accurate it is.

The passage supports this directly. The author gave three examples, each one “more general” than the next, so that wording maps nicely.

(C) …become more temporally remote.

The first part maps really well, but how far into the future the prediction goes isn’t mentioned in the passage, so “temporally remote” doesn’t map to anything stated.

(D) The more detailed and complete…

See (A).

(E) …unlikely to be accurate.

Liar! The passage says predictions based on “birth rates” have “reasonable accuracy” in at least that one case. That a “general trend” for sure. Never pick an answer that contradicts the passage.

(B) is the correct answer.