Asbestos is mainly used in which of the following materials?

Asbestos was primarily used for its exceptional insulating properties and its ability to resist fire. This makes thermal insulation and fireproofing materials the main applications for asbestos. In construction, asbestos was often incorporated into insulation products, pipe insulation, boiler insulation, and various types of fireproofing materials to protect structures and reduce the risk of fire.

The other options, while relevant to construction, do not primarily involve the use of asbestos. Electrical wiring typically utilizes materials such as copper or aluminum for conductivity and insulation materials that do not contain asbestos. Wood flooring and metal roofing also do not have a historical association with asbestos, as these materials evolved separately in terms of safety standards and insulation technology. Thus, option B is the most accurate assessment of where asbestos was mainly utilized.