The lower left corner is the answer.
Angle 1 is congruent to angle 5 because they are alternate interior angles (assuming AB || DE)
They are on the inside of the parallel train tracks. By "train tracks" I mean the horizontal lines AB and DE. So they are considered interior angles. They are on alternate sides of the transversal AE. Angle 1 is on the right side while angle 5 is on the left side. These two facts are why they are considered alternate interior angles.
