Any decision tree that sorts n elements has height ..............
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Correct answer: (C) Ω(n lg n)
Explanation
A binary tree of height h has at most 2ʰ leaves. Sorting n elements requires at least n! leaves, so n! ≤ 2ʰ, giving h ≥ lg(n!) ≥ (n/2) lg(n/2) = Ω(n lg n).