Which statement about insulators is true?

• A. They cannot hold electrons stationary.
• B. They are the only materials that conduct electricity.
• C. They are poor conductors of heat but not related to electricity.
• D. Insulators are the only materials that can hold electrons stationary.

Answer: (D)

The main idea is that insulators keep electric charges from moving freely because their electrons are tightly bound to atoms. When an electric field is applied, only tiny, localized shifts of electrons occur around their atomic or molecular bonds; there aren’t free carriers that can drift through the material. That lack of freely moving charge carriers means current is very small, so the electrons stay essentially stationary within the material. That’s why insulators are poor conductors of electricity.

Because of that, the statement that insulators cannot hold electrons stationary isn’t accurate. And they aren’t the only materials that can hold electrons in place; metals don’t hold them stationary, as their electrons move freely and conduct electricity. Also, insulators are poor conductors of both electricity and heat, so saying they’re only related to heat conduction isn’t right. The point about insulators being the only materials that can hold electrons stationary aligns with the basic description of localized electrons, making it the best fit among the options.