When constructing parallel lines, how can you be sure the lines you constructed are parallel?

When constructing parallel lines, how can you be sure the lines you constructed are parallel?

A. See if the distance between the two lines is consistent with a compass.
B. Make sure the lines intersect at right angles with the corner of a piece of paper.
C. Measure each of the angles with a straightedge.
D. There is no way to ensure you have constructed parallel lines.