Answer: 1 and 5, 2 and 6, 3 and 7, 4 and 8.
Step-by-step explanation:
The pairs of two angles given above follow the "corresponding angles theorem".
Hence, angles 1 and 5, 2 and 6, 3 and 7, 4 and 8 are congruent that prove that line a is parallel to line b.