Explanation:
The statement in question states that there are no rules for designing a truss, but there are rules for designing bridges. The correct answer is option B, which means that the first part of the statement is false and the second part is also false.

Designing a truss:
A truss is a structural framework that consists of straight members connected at joints. Trusses are commonly used in engineering and construction to support loads such as the weight of a roof or a bridge. While there may not be specific rules for designing a truss, there are certainly principles and guidelines that need to be followed to ensure the structural integrity and stability of the truss. These principles include:

1. Analysis of loads: The first step in designing a truss is to analyze the loads that the truss will be subjected to. This includes considering the weight of the structure, any live loads such as people or vehicles, wind loads, and seismic loads. The truss must be designed to safely support these loads without excessive deflection or failure.

2. Material selection: The choice of materials for the truss is important to ensure its strength and durability. Common materials used for truss construction include steel, timber, and aluminum. The material must be able to withstand the loads and environmental conditions that the truss will be exposed to.

3. Truss configuration: The configuration of the truss, including the arrangement and size of the members and the connections between them, is crucial for its stability and load-bearing capacity. Various truss configurations, such as the Pratt truss, Warren truss, and Howe truss, have different advantages and limitations, and the appropriate configuration should be chosen based on the specific requirements of the project.

4. Structural analysis: Once the truss configuration is determined, it is important to perform structural analysis to ensure that the truss can safely carry the imposed loads. This analysis involves calculations to determine the internal forces and stresses in the truss members, as well as deflections and deformations. Finite element analysis (FEA) software is commonly used for this purpose.

Designing a bridge:
The second part of the statement is also false. There are indeed rules and guidelines for designing bridges. Bridges are complex structures that must safely support the weight of vehicles, pedestrians, and other loads while spanning across rivers, valleys, or other obstacles. The design of a bridge involves several considerations, including:

1. Structural analysis: Similar to truss design, a bridge must undergo structural analysis to ensure its stability and load-bearing capacity. This analysis considers the forces and stresses that the bridge will experience, including dead loads, live loads, wind loads, and seismic loads.

2. Material selection: The choice of materials for the bridge depends on factors such as span length, anticipated loads, and environmental conditions. Common bridge materials include steel, concrete, and composite materials. The material must have sufficient strength, durability, and resistance to corrosion.

3. Bridge type and configuration: Different types of bridges, such as beam bridges, arch bridges, and suspension bridges, have different structural characteristics and requirements. The selection of the appropriate bridge type and configuration depends on factors such as span length, terrain, and budget.

4. Geotechnical considerations: Bridges often require foundations to support their weight. Geotechnical investigations are conducted to assess the soil and rock conditions at the bridge site, which helps determine the appropriate foundation design, such as