Fiberglass is typically used for insulation.

• A. Fiberglass
• B. Concrete
• C. Steel
• D. Brick

Answer: (A)

Insulation materials are chosen for their ability to slow heat transfer and be practical to install. Fiberglass achieves this well because its fine glass fibers trap air, creating very low thermal conductivity. It’s also noncombustible and remains effective across a range of temperatures, making it a staple for insulating walls, attics, and ductwork.

The other options are primarily structural or masonry materials. Concrete and brick are dense and store or conduct heat rather than prevent rapid temperature change, while steel conducts heat easily and isn’t used to insulate. So fiberglass best fits the purpose of insulation among the choices.