The correct answer is D) stranded wire increases their flexibility over solid wire and reduces skin effect losses. Stranded wire is composed of multiple smaller individual wires twisted together, rather than a single solid conductor. This design provides greater flexibility compared to a solid wire of the same overall diameter. The increased flexibility is advantageous for electrical cables that need to be bent, routed, or installed in confined spaces. Additionally, stranded wire construction helps reduce skin effect losses at higher frequencies. The skin effect causes the electric current to flow mainly at the surface of the conductor, but the stranded design helps mitigate this issue, improving the overall current-carrying capacity of the cable. The other answer choices are incorrect because they do not fully explain the primary reasons for using stranded wire in electrical applications.