Answer:
D. BC ≅ EF
Explanation:
ASA means you're trying to show congruence by showing two angles A..A and the segment between them ..S.. are congruent. The figure shows two congruent angles. What remains is to show the segments between are congruent.
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In ∆ABC, the marked angles are B and C, so the segment between them is BC.
In ∆DEF, the marked angles are E and F, so the segment between them is EF.
These are the segments that need to be shown congruent if you're using ASA.
BC ≅ EF