Which diagram shows parallel lines cut by a transversal?

Only the third model shows parallel lines cut by a transversal. 

We can solve this problem by using some properties that parallel lines cut by a transversal have. First of all, corresponding angles are congruent, and since the angles in figure 1 are corresponding but not congruent, that means that figure one is out. 

In addition, in figure two, alternate exterior and interior angles of parallel lines intersected by a transversal are congruent, so since they are not in the picture, that means that this figure is also out. 

Figure three is correct because since those are same side interior angles, they need to be supplementary for those to be two parallel lines intersected by a transversal. Since they do, in fact, add up to 180°, that means that the answer is figure three.