Final answer:
Skew lines are lines that do not intersect and are not parallel. The pairs (a, b), (c, b), and (e, c) are skew lines.
Step-by-step explanation:
Skew lines are lines that do not intersect and are not parallel. To determine which lines are skew, we need to identify pairs of lines that satisfy these conditions. Looking at the given options, the pairs (a, b), (c, b), and (e, c) are skew lines because none of them intersect and they are not parallel. Therefore, the correct answer is D. e and c.