Question

Given ∠8≅∠12 .

Answer 1

Your answer would be B
When you have two angles, and want to know which lines must be congruent, you have to look at the transversal first. The two angles will share a side which is the transversal, and then their other side is one of the parallel lines. 
The converse of the corresponding angles theorem states that If corresponding angles are congruent, then the lines are parallel.

Answer 2

Answer:

B) a∥b, Converse of the Corresponding Angles Theorem