Answer
Line AB corresponds to line PQ
Line BC correspond to line QR
Line CA corresponds to line RP
Work Step by Step
1. Congruent angles marked on the diagram, correspond one to each other.
$\angle B - \angle Q$ ; $\angle A - \angle P$; and $\angle C - \angle R$
2. The key here is to go around the triangles starting with the corresponding angles. Then, for the first pair, you can went from the doubled lined angle to the single lined angle. Eventually, you will get corresponding lines as following:
Line AB corresponds to line PQ
Line BC correspond to line QR
Line CA corresponds to line RP
