Answer :
In the context of patented railroad bridge designs that were quick and inexpensive to build, the correct answer is:
A) Truss
Explanation:
1. Truss bridges are known for their efficiency in construction, making them quick and cost-effective to build.
2. Truss bridges can be constructed using wood or iron, both materials commonly used in early railroad bridge designs.
3. The triangular truss framework in truss bridges provides strength and stability, making them a popular choice for railroad bridges due to the heavy loads they need to support.
4. Truss bridges are versatile and can span long distances, making them suitable for railroad applications where long spans are common.
