Which conclusion of the following statement must always be true?
 “If angle 1 and angle 2 are alternate interior angles of parallel lines cut by a transversal, then”
 angle 1 and angle 2 are supplementary.
 angle 1 and angle 2 are complementary.
 angle 1 and angle 2 are a linear pair.
 angle 1 is congruent to angle 2.