The lines that are parallel lines are (a) Line a & Line b
Determining which lines are parallel
From the question, we have the following parameters that can be used in our computation:
The graph
By definition
Lines that intersect can never be parallel lines
using the above as a guide, we have the following:
The lines (a) and (b) are parallel lines
This is so because these lines never intersect
Hence, the lines that are parallel lines are (a) Line a & Line b