Sara draws three pairs of parallel lines with a 3rd line intersecting each pair. She measures some pairs of alternate exterior angles as shown. What is a reasonable conjecture for Sara to make by recognizing a pattern and using inductive reasoning?
 a) When a pair of parallel lines are intersected by a third line, alternate exterior angles are supplementary. 
b) When a pair of parallel lines are intersected by a third line, alternate exterior angles are acute. 
c) When a pair of parallel lines are intersected by a third line, alternate exterior angles are congruent. 
d) When a pair of parallel lines are intersected by a third line, alternate exterior angles are complementary