Question

The figure below shows line PQ parallel to line RS. The parallel lines are cut by the transversal XY. Which fact is used to prove that angles PMN and MNS are congruent?
Answer

If two lines intersect, the vertical angles are supplementary.

All angles equal to the same measure are complementary.

All pairs of alternate interior angles have the same measure.

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