Final answer:
The transitive property of parallel lines can be used to prove that p║q in the fewest number of steps.
Step-by-step explanation:
The property that could be used to prove that p║q in the fewest number of steps is the transitive property of parallel lines. According to this property, if a line is parallel to a second line, and the second line is parallel to a third line, then the first line is parallel to the third line. Therefore, if we can show that line p is parallel to line q, and line q is parallel to line r, then we can conclude that line p is parallel to line r as well.