Which choice completes the text with the most logical and precise word or phrase?
Answer:Although nineteenth-century physicist Lord Kelvin argued that the Earth's cooling rate placed a strict upper limit on its age, his calculations relied on the assumption that heat was transferred solely through conduction in a solid interior. The subsequent discovery of radioactivity and mantle convection proved that the Earth's interior actively generates and circulates heat, rendering Kelvin's once-authoritative estimates 【erroneous】.
Answer
The correct answer is a word such as 'erroneous,' 'flawed,' or 'untenable' that indicates Kelvin's estimates were incorrect.
The passage explains that Kelvin's estimates of the Earth's age relied on an assumption (conduction only in a solid interior) that was later proven false by the discovery of radioactivity and mantle convection. Because the basis of his calculations was incorrect, his estimates were rendered incorrect. Therefore, words indicating inaccuracy or invalidity, such as 'erroneous,' 'flawed,' or 'untenable,' logically complete the context.
Step-by-Step Solution
Key Concept
Determining high-utility academic vocabulary through logical contrast and contextual evidence.