Answer : The correct option is, (A) Alternate interior angles of parallel lines are congruent.
Step-by-step explanation :
Exterior angle theorem : It is defined as the angle formed when we extend the side of a triangle is equal to the sum of its non-adjacent angles.
In the given figure, ∠1 = ∠2 +∠C
Alternate interior angles : It states that when two parallel lines are cut by a transversal, then the pairs of alternate interior angles are congruent.
In the given figure, ∠1 ≅ ∠A and ∠3 ≅ ∠C
Hence, the correct option is, (A)