The figure below shows two parallel lines cut by a transversal: which statement is true about ∠1 and ∠2? a: they add up to 90 degrees, because they are a pair of complementary angles. b: they add up to 180 degrees, because they are a pair of complementary angles. c: they add up to 180 degrees, because they are a pair of supplementary angles. d: they add up to 90 degrees, because they are a pair of supplementary angles.