Concept:An insulator is a material that resists the flow of electric current because it has very few free electrons.
Explanation:Rubber is a non-metallic material with electrons tightly bound to their atoms.
These electrons are not free to move, so rubber does not allow electric charge to flow through it easily.
This makes rubber an excellent insulator.
In contrast, silver and copper are metals with many free electrons.
These free electrons move readily, making silver and copper very good conductors of electricity.
Water, especially when it contains dissolved salts or impurities, also conducts electricity because the ions in the water carry charge.
That is why rubber is commonly used to coat electrical wires and protect users from electric shock.
Therefore, among the given options, rubber is the material that acts as a good insulator.
Answer:C. Rubber