What advantage do bushings provide when used with conduit fittings?

Bushings serve a crucial role when used with conduit fittings by providing protection to the wires from abrasion at the ends of the conduit. When wires are pulled through the conduit, especially in applications where flexibility and movement may occur, they can come into contact with the sharp edges of the conduit openings. Bushings are designed to cover these edges and create a smooth surface, preventing wear and tear on the insulation of the wires. This not only prolongs the life of the wiring but also helps to maintain safety by reducing the risk of short circuits that could arise from damaged insulation.

The other options, while relevant to electrical installations, do not accurately describe the primary function of bushings. The grounding of conduits, waterproofing capabilities, or support for vertical conduits involve other components or methods designed specifically for those purposes. Bushings are specifically focused on safeguarding the wire insulation from potential damage during installation or use, making option B the most appropriate choice.