Answer:
SAS
Step-by-step explanation:
we know that
Triangles are congruent by SAS, if any pair of corresponding sides and their included angles are equal in both triangles
so
In this problem
we have that
the pair of corresponding sides AB with DC and AD with DA and their included angles ∠ BAD with ∠CDA are equal
therefore
Triangle ABD is congruent with triangle DCA by SAS congruency theorem
