Which organization is headquartered in Northbrook, Illinois?

Underwriters Laboratories Inc., commonly known as UL, is a global safety science organization headquartered in Northbrook, Illinois. Established in 1894, UL focuses primarily on safety testing, certification, and standards development for a wide range of products and industries, including fire protection and building materials. The organization's significant contributions to safety standards make it a critical player in the firestop industry, ensuring that products meet rigorous safety and performance criteria.

While the other options represent different organizations, they are not based in Northbrook, Illinois. Internet Testing Services, for instance, operates in various capacities related to testing and certifications but is not noted for being headquartered in that location. Omega Point Laboratories is involved in laboratory testing but does not have the same recognition or history as UL. Lastly, Underwriters Laboratories of Canada, although related, is a separate entity that operates under UL's broader umbrella but is based in Canada, not Illinois. This distinction underlines why Underwriters Laboratories Inc. is the correct choice in this context.