The correct option is "Non-parallel and non-intersecting shafts".

To understand why this is the correct answer, let us look at the geometry and function of a worm gear set:
1. Components: A worm gear set consists of a worm (which resembles a screw) and a worm wheel or gear (which resembles a spur gear).
2. Shaft Orientation: The shafts of the worm and the worm wheel are positioned perpendicular to each other in space. However, they do not lie in the same plane. Because they are perpendicular but in different planes, their axes of rotation are non-parallel.
3. Non-intersecting: Since the axes lie in different offset planes, they do not cross or meet at any point, making them non-intersecting.
4. Application: Therefore, a worm gear set is uniquely designed to transmit rotary motion and power between two shafts that are skew to each other, meaning they are both non-parallel and non-intersecting.