SAT Question 6c64a8f3: Words In Context answer and explanation

English - Words In Context - Fill In Blank Single Word
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Ecologist Exequiel Ezcurra and colleagues found that the inhabitants of the Mexica empire used natural landmarks to track time with a high degree of ______. By observing the sun’s position in relation to various points on the mountains surrounding the Basin of Mexico, the Mexica were able to precisely identify the dates when significant events such as solstices occurred.
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Difficulty:Medium
Which choice completes the text with the most logical and precise word or phrase?