In the figure below AB is parallel to CD
Which statement proves that angle3 cong angle7.

If two parallel lines are cut by a transversal, the alternate interior angles are congruent.

If two parallel lines are cut by a transversal, the alternate exterior angles are congruent.

If two parallel lines are cut by a transversal, the corresponding angles are congruent.

If two parallel lines are cut by a transversal, the vertical angles are congruent.