Electrical conductivity is a measure of a material's ability to conduct electric current. Materials are classified based on their conductivity: - Insulators have very low conductivity, resisting the flow of charge (e.g., rubber, plastic, glass). - Semiconductors have conductivity between that of insulators and conductors, which can be significantly altered by temperature, doping, or external fields (e.g., silicon, germanium). - Metals (conductors) have high conductivity, allowing charge to flow easily (e.g., copper, silver, gold). Arranging these in ascending order of conductivity means starting from the lowest conductivity to the highest. Therefore, the correct sequence is Insulators