In general, how far apart are the roof joists for the lower roof at the Veterinary Center?

The spacing of roof joists is an essential consideration in building design as it affects both structural integrity and material efficiency. In this scenario, the correct answer indicates that the roof joists for the lower roof at the Veterinary Center are positioned 5 feet apart. This spacing is commonly used in many construction applications, particularly in commercial and institutional buildings like veterinary centers, where a balance between stability and material economy is crucial.

Proper joist spacing helps distribute loads effectively while allowing adequate room for insulation and potentially mechanical systems, which may be necessary for the building's function. Moreover, the choice of 5 feet typically meets standard building codes and practices, which are aimed at ensuring safety while optimizing resources.

In this case, the other options do not align with typical construction practices for the overall design requirements and intended use of the building. Hence, choosing 5 feet reflects a pragmatic approach that adheres to structural norms and safety considerations in the construction of the Veterinary Center.