Which of the following is an example of a good insulator?

Plastic is an example of a good insulator because it has a high resistance to the flow of electric current and heat. Insulators are materials that do not conduct electricity well, meaning they allow very little electrical charge to pass through them. This characteristic makes plastic widely used in various applications, such as electrical wiring and household items, where it is essential to prevent the unintended flow of electricity and to ensure safety.

In contrast, metals like gold, copper, and aluminum are excellent conductors of electricity and heat. They allow electric charge to move freely, which makes them unsuitable for applications where insulation is required. For instance, gold and copper are often used in electrical connections and components due to their conductive properties. Aluminum also has high conductivity, making it ideal for electric transmission lines and other conductive applications. Therefore, plastic stands out as a good insulator among the options provided.