Which of the following best describes an insulator?

An insulator is best described as a substance that reduces heat transfer. Insulators are materials characterized by their ability to resist the flow of heat. This property is crucial in various applications, such as keeping buildings warm in winter and cool in summer, or preventing heat loss in electrical systems. Materials like rubber, glass, and certain plastics serve as effective insulators because their molecular structure limits the movement of heat energy.

The other options do not accurately describe the characteristics of an insulator. A device that increases electron flow pertains to conductors rather than insulators, which impede electron movement. A fluid that enhances chemical reactions does not relate to the thermal conductivity properties of insulators. Lastly, a mesh that filters particles is unrelated to heat transfer and instead concerns separation techniques, such as sieving. This highlights the specific role of insulators in controlling thermal energy rather than engaging in electrical conduction or chemical interactions.