Final answer:
Vertical angles are formed when two lines intersect and are opposite each other at the intersection. In the case of parallel lines q and r cut by the transversal t, all angles formed at the intersections are vertical angles.
Step-by-step explanation:
Vertical angles are formed when two lines intersect. In the case of parallel lines q and r cut by the transversal t, the angles that are opposite each other at the intersection are vertical angles. These angles are congruent, meaning they have the same measure. Therefore, all angles formed by the intersections of q, r, and t are vertical angles.