Which congruence theorem would complete the proof shown?
SSS
SAS
ASA

In the figure, AB || DC and AC is a transversal.
So, ∠2 = ∠3
∠1 = ∠4 (alternate interior angles)
Now, in triangles ACB and ACD,
∠2 = ∠3
∠1 = ∠4
AC = AC (common)
Therefore, Δ ACB ≅ Δ ACD (ASA Rule)