Early explorers proposed that every channel crossing a desert plateau had been formed exclusively by wind erosion. Satellite surveys later identified branching feeder channels and mineral deposits that can form only when water flows intermittently, though wind likely reshaped some channels afterward. In light of both the survey findings and the continuing evidence of wind erosion, the explorers’ explanation, as originally formulated, is _____.
Which choice completes the text with the most logical and precise word or phrase?
For a Words in Context question, identify qualifiers that control the scope of a claim, such as “every,” “some,” or “exclusively.” Then determine whether later evidence supports the claim, merely adds information to it, or directly contradicts it. When multiple choices have the correct general tone, select the one that most precisely captures that logical relationship rather than a broader description that is only loosely true.
Hints
Notice the absolute language
Focus on “every” and “exclusively.” Determine what those words require to be true about all the channels.
Compare omission with contradiction
Ask whether the surveys merely add a detail that the explorers did not mention or whether they conflict with something the explorers explicitly claimed.
Interpret the concession carefully
The evidence that wind reshaped some channels supports only part of the original view. Consider whether that limited support preserves the explanation in its original, categorical form.
Step-by-step Explanation
Identify the scope of the original claim
The explorers did not merely suggest that wind affected the channels. They claimed that every channel was formed exclusively by wind, thereby ruling out any role for water.
Interpret the new evidence
The feeder channels and mineral deposits can form only when water flows. Therefore, the surveys establish that water contributed to the formation of at least some channels, directly conflicting with the explorers’ categorical claim.
Account for the concession
The passage acknowledges that wind probably reshaped some channels. This concession preserves part of the explorers’ view, but it does not rescue their claim that wind formed every channel without any contribution from water.
Choose the most precise description
“Indefensible” means unable to be justified or maintained. Because the original explanation explicitly excluded a process that the evidence proves occurred, it is indefensible as formulated. Merely calling it incomplete would understate the problem: it did not simply omit water but effectively denied water any role.