Final answer:
The insulating material for a cable should have high mechanical strength, low cost, and high dielectric strength, but not high expense, which is not desirable due to increased costs.option B.
Step-by-step explanation:
The insulating material for a cable should have all except high expense. Insulating materials are chosen based on several properties such as high mechanical strength, low cost, and high dielectric strength. The latter refers to the maximum electric field strength above which the material begins to break down and conduct, thus it's crucial for maintaining insulation under high voltage conditions. Conversely, a high expense is not desirable as it increases the overall cost of cable production and installation.
Materials like copper are commonly used for wiring due to their low resistivity, high tensile strength, and high ductility, which make them excellent conductors. While different materials may serve as alternatives to copper for various applications, they will also have a unique set of advantages and disadvantages. Factors like the dielectric constants, thermal stability, and flexibility should be considered when selecting an insulating material for specific uses.