Fill in the blank with the phrase that makes the proof statement true.

lines a and b are parallel. angle 1 is congruent to angle 3 by the corresponding angles postulate. angle 1 is supplementary to angle 2 because they form a linear pair. by the substitution property.

a. angle 3 is congruent to angle 2
b. angle 1 is congruent to angle 2
c. angle 3 is supplementary to angle 2
d. line a is parallel to line b