A main idea question tests whether you can say what the whole passage says about its topic. Name the topic, then ask what the evidence says about the opening view. At a change in direction, follow the point after the turn, because later evidence may challenge or limit that view. Predict one sentence that explains what the findings show together. Wrong choices often repeat a true finding without covering the whole point.
Hints
- Hint 1
Start with the historians’ opening classification. Ask which later findings test that way of classifying marginal numbers.
- Hint 2
The comparison mentions both latitude and copying traditions. Check why both details matter to the finding.
- Hint 3
After Yet, follow the calculations from one copy to the next. Ask how those changes affect the opening classification.
Step-by-step
Follow the evidence past the turn
Step 1Name the topic and starting view
Historians classify numbers added in the margins as deviations from the works’ texts, so their starting view labels calculations by location. For the main idea, what does the comparison add? Calculations cluster at ports sharing similar latitudes even in manuscripts from unrelated copying traditions, which suggests readers adjusted tables for local needs.
- Step 2
Build the point after the turn
Yet manuscript sequences show shifts us from local observations to later copies. What changes in those copies? Some adjustments were later copied into the main text, while main-text calculations were shifted to a margin in a later copy. So a calculation’s place isn’t a lasting sign of whether it belongs to the text, because recopying can change its place. We can predict the point: local changes and later copying worked together to shape the handbooks.
- Step 3
Set aside claims that miss the point
Which choices miss part of that point or add claims the passage doesn’t support? The geographic distribution is only a detail because it leaves out recopying, including adjustments later copied into the main text. The phrase cannot reliably determine goes too far because changing location doesn’t prove an adjustment’s origin can’t be traced. And primarily valued goes past the text by saying what mattered most to scribes when the passage doesn’t tell us.
- Step 4
Connect the claim to the opening rule
The choice about a fixed marker of its textual status questions the opening label. Calling marginal numbers deviations from the works’ texts treats them as outside the work, even though copying can later place them inside it. This choice links that labeling problem to both local use and recopying, so it explains how later versions took shape. Choice B.