Mark is asked to prove that ∠4≅∠6, given that AB∥CD, as shown in the diagram above.

Mark's proof is shown in the table below.

Which reason supports the statement Mark made in step 2 of his work?


A
Vertical angles are congruent.


B
Supplementary angles are congruent.

C
Corresponding angles formed by parallel lines are congruent.

D
Alternate interior angles formed by parallel lines are congruent.