4
12
I'm pretty sure it is 12 pairs of parallel lines.
3 sets of four mutually parallel lines.
Yes: three sets of four.
A cuboid has 3 quartets of parallel lines. Each quartet gives rise to six pairs. So, in all there are 18 pairs of parallel lines.
4 parallel edges
Three sets of four each.
A cuboid has 12 pairs of parallel lines. Each pair consists of 4 edges that run parallel to each other, with three dimensions (length, width, and height) creating edges in parallel orientations. Thus, there are a total of 12 edges, grouped into 6 sets of 2 parallel edges each.
3 pairs
Three.
21
3 pairs