Which among the following is NOT an insulator?

Mercury

The correct answer is option 3. Mercury.

Mercury is a liquid metal at room temperature and does not inhibit the flow of electricity. In fact, it is a conductor of electricity. Therefore, mercury is not an insulator.

Ebonite (option 1), dry paper (option 2), and glass (option 4) are all examples of insulators. Insulators are materials that do not allow electric current to flow easily through them. They have high resistance to the flow of electrical charge and are used to separate conductive materials to prevent the flow of electricity.