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.
The appropriate choice is ...
◉ ∠2 and ∠3
