What is a manufactured product made up of standard sized wood members connected with metal plates, typically spanning 24 to 40 ft?

The correct choice is the trussed wood joist. This type of manufactured product is specifically designed to efficiently use standard-sized wood members, usually constructed in a triangular pattern which provides strength while minimizing material use. The use of metal plates to connect these wood members is a characteristic feature, allowing for rapid assembly and increasing load-bearing capabilities.

Trussed wood joists are commonly utilized in floor and roof systems where long spans are necessary, typically ranging from 24 to 40 feet. This span range makes them particularly useful in larger residential and commercial structures, where traditional solid beams would be too heavy or expensive to use.

In contrast, while other options like box beams and open-web steel joists are also used in construction, they do not specifically incorporate the same combination of wood members and metal plates or serve the same function in a lightweight, cost-effective manner over the lengths mentioned. A waffle slab, on the other hand, refers to a type of reinforced concrete slab system that differs entirely in materials and structural approach.