Central Ideas questions ask for the main point of a passage. Details questions ask what the passage directly states. Both reward reading what's actually on the page — not what's plausible in the real world.
Main idea = the claim every sentence supports. If a choice is true of only one sentence, it's a detail, not the central idea.
How to win these
- For central ideas: after reading, say the point in your own words, then find the choice closest to it.
- Too narrow (only part of the passage) and too broad (bigger than the passage) are the two classic wrong-answer shapes.
- For details: the answer is a paraphrase of something explicitly stated. If you can't point to the line, it's wrong.
Trap: A choice that's factually true and on-topic but never stated in the passage. On the SAT, "true in reality" ≠ "supported by the text."