Answer:
D. ASA
Explanation:
In triangles ABC and ADC,
- Angles BCA and DAC are congruent (from the diagram);
- Angles BAC and DCA are congruent (from the diagram);
- AC is congruent AC (by reflexive property).
So, the triangles ABC and CDA are congruent by ASA postulate.
ASA (Angle-Side-Angle) postulate states that if two angles and the included side of one triangle are congruent to two angles and the included side of another triangle, then the triangles are congruent.