Which astronomical measurement enabled Al-Biruni to estimate the Earth's circumference in the 11th century?

💡 Explanation

When observing solar altitude at different locations, Al-Biruni employed triangulation because differences in angular height combined with known distances allow for estimation of Earth's curvature and circumference. Therefore, option B is correct, rather than lunar parallax, stellar position ,or planetary conjunctions, which were used for other astronomical calculations.

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