Which statement proves that∠3≅∠7?
a.) If two parallel lines are cut by a transversal, the alternate interior angles are congruent.

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

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

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