If p is parallel to q, which pair of angles must be congruent?

Vertical angles are congruent whether the lines are parallel or not.

Corresponding angles are congruent.

Alternate interior and alternate exterior angles are congruent.

1 & 4, 2 & 3, 3 & 6, 4 & 5, 1 & 8, 2 & 7, 5 & 8, 6 & 7, 3 & 7, 1 & 5, 2 & 6, 4 & 8

I think I got all of them!