2. On the same plane, a straight line intersects one of the two parallel lines, so this straight line must intersect the other side of the parallel line.
3. Two intersecting straight lines cannot be parallel to the third straight line in the same plane, because the third straight line must intersect with one of the first two straight lines.
4. Two straight lines intersect, and the intersection number is 1. Two straight lines are parallel, and the intersection number is 0.
5. In the same plane, there are only two positional relationships between two straight lines: intersecting or parallel. But real space is three-dimensional. Just think about the positional relationship between two straight lines in space.
A:
Three relationships:
1, intersection,
2, parallel,
3. Not parallel or intersecting (not on the same plane).