B

Step 1: ∠B ≅ ∠C[The base angles of isosceles triangle are congruent.]

Step 2:



Step 3: If the two angles and the non included side of one triangle are congruent to the two angles and the non included side of another triangle, then the two triangles are congruent.[AAS Theorem.]

Step 4: ΔABD ≅ ΔACD[AAS Theorem.]