Question 114·Hard·Inferences
Because tree-ring chronologies rarely extend beyond 10,000 years, paleoclimatologists often turn to ice cores to reconstruct older climate patterns. Ice cores, however, cannot be taken from every mountain glacier because some are too thin to preserve yearly layers. To address this gap, Sánchez et al. (2022) analyzed stalagmite growth bands from caves near the glaciers and found that these mineral deposits could extend the temperature record a further 80,000 years, which tree rings and ice cores together could not accomplish because ______
Which choice most logically completes the text?
For “most logically completes the text” items, use the words right before the blank to identify the relationship (here, “because” signals a cause). Then match the choice that restates the passage’s explicitly stated constraints, and avoid options that introduce a different-sounding limitation not mentioned in the text.
Hints
Use the connector
The word “because” means the blank must give a cause explaining why tree rings + ice cores can’t achieve the 80,000-year extension.
Reuse the passage’s stated limits
Identify the limitation for tree rings (time span) and the limitation for mountain ice cores (some glaciers can’t preserve yearly layers).
Watch for near-miss science claims
Some choices will sound scientifically reasonable (melting, dating problems, polar ice sheets), but the correct answer must match the exact limitation stated in the passage.
Step-by-step Explanation
Determine what the blank must do
The sentence ends with “could not accomplish because ______,” so the blank must provide the reason tree rings plus ice cores still fall short.
Locate the two limitations stated in the text
The text directly states:
- Tree rings: they “rarely extend beyond 10,000 years.”
- Ice cores (from mountain glaciers): they can’t be taken everywhere because some glaciers are “too thin to preserve yearly layers.”
Eliminate choices that change the passage’s stated limitation
The correct option must match the passage’s specific obstacle for ice cores (thin glaciers can’t preserve yearly layers), not a different issue like melting, polar-only extraction, or general dating difficulty.
Choose the option that restates both stated constraints
The only choice that directly combines the passage’s two stated limits is:
tree-ring chronologies rarely extend beyond 10,000 years and some mountain glaciers are too thin to preserve yearly layers.