The correct answer is A. Conductance.
Conductance is the ability of a material to allow the flow of electricity. It is measured in siemens (S). The higher the conductance, the better the material is at conducting electricity.
Resistance is the opposite of conductance. It is the ability of a material to resist the flow of electricity. It is measured in ohms (Ω). The higher the resistance, the worse the material is at conducting electricity.
Reluctance is a measure of how difficult it is to magnetize a material. It is measured in ampere-turns per weber (AT/Wb). The higher the reluctance, the harder it is to magnetize the material.
Thermal conductivity is a measure of how well a material conducts heat. It is measured in watts per meter per kelvin (W/m/K). The higher the thermal conductivity, the better the material is at conducting heat.
In conclusion, all good conductors have high conductance. This means that they are good at allowing the flow of electricity.