What is characterized by lightweight structural supports for roofs or floors?

The correct answer is trusses, which are specifically designed as lightweight structural supports for roofs and floors. Trusses are highly efficient structural elements that utilize a triangulated system of members, allowing them to span long distances without the need for additional supports. This design maximizes strength while minimizing the amount of material needed, making them both economical and effective for construction.

In contrast, beams are horizontal supports used to carry loads across open spaces, but they are typically heavier and require more robust support systems than trusses. Frames consist of a combination of beams and columns that create a skeletal structure for buildings, often providing vertical and lateral support but lacking the specific lightweight characteristic of trusses. Columns are vertical structural elements that primarily support loads from above, but they do not encompass the design principles associated with lightweight supportive frameworks like trusses do.