Let's talk about the choices ◯ ∠4 and ∠5 . . . . . . . . these are complementary angles whose sum is 90° ◯ ∠7 and ∠9 . . . . . . . . these are vertical angles, equal to each other ◯ ∠2 and ∠3 . . . . . . . . these are supplementary angles that together form a straight line. They are a linear pair. ◯ ∠1 and ∠2 . . . . . . . . these are "adjacent" angles in the quadrilateral that also includes ∠9 and ∠10.
