Geometry

Question Analysis:
This problem asks for the missing third condition to apply the ASA postulate.

Key Concept Explanation:
For ASA, we need:
Two angles in one triangle congruent to two angles in another.
The included side between these angles congruent.

Step-by-Step Solution:
Given ∠A ≅ ∠D and AB ≅ DE, we need another angle adjacent to AB (the included side).
∠B ≅ ∠E satisfies this requirement, forming ASA.

Option Analysis:
A (∠B ≅ ∠E) → Correct (This completes ASA by providing the second angle).
B (AC ≅ DF) → Incorrect (Adding a side does not form ASA, but could suggest SAS).
C (BC ≅ EF) → Incorrect (Three sides would follow SSA, not ASA).
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