Answer:
The correct option is 2.
Explanation:
Given information: DC║AB, DC=AB.
If a transversal line intersect two parallel lines, then the alternative interior angles are equal.
In triangle ABC and CDA,
(Given)
(Alternative interior angles)
(Common side)
Two corresponding sides and their including angle are equal.
By SAS postulate of congruent triangles,

Since both triangles are congruent by SAS postulate, therefore the correct option is 2.