Identify the reason that justifies the following statements. 19) 1=~4
20) 2+4+5 = 180
21) 5+7=180
22) 4+2=7
23) If CA bisects DCB, then 1 =~ 2
24) 3+7=180

Possible reasons:

A. Triangle exterior angle theorem
B. Vertical angles are congruent
C. Angle addition postulate
D. If lines are parallel, then alternate interior angles are congruent
E. If lines are parallel, then corresponding angles are congruent
F. If lines are parallel, then same side interior angles are supplementary
G. Definition of midpoint
H. Definition of angle bisector
I. The sum of the angles of a triangle is 180