Which choice completes the text with the most logical and precise word or phrase?
Answer:For decades, planetary scientists assumed that the surface of the dwarf planet Ceres was geologically inert, frozen solid and unchanging. However, recent data collected by the Dawn spacecraft revealed localized deposits of sodium carbonate, indicating that salty water had recently erupted from an underground reservoir. This unexpected discovery suggests that Ceres, far from being a dormant relic, has exhibited active cryovolcanism in its recent history, thereby 【challenging】 the long-held assumption that small celestial bodies lack the internal heat necessary for geological activity.
Answer
The blank should be filled with a word such as 'challenging' or 'undermining' to describe how the new discovery of cryovolcanism contradicts or weakens the previous assumption that Ceres was geologically inert.
The sentence describes how new evidence of geological activity affected a previous assumption that Ceres was geologically inert. Because the new evidence directly opposes the old assumption, a word meaning to dispute, weaken, or call into question is needed. 'Challenging' and 'undermining' are precise academic choices that fit this context.
Step-by-Step Solution
Key Concept
Determining the logical relationship between new evidence and a historical hypothesis, and selecting a precise academic term to describe that relationship.