Of the total number of bridges, which percentage is classified as rural in the US?

Answer: B — 72%

In the United States, a significant percentage of bridges are classified as rural due to the vast expanses of rural areas that require transportation infrastructure. The correct choice, which indicates that 72% of total bridges are rural, reflects the reality of infrastructure distribution where a majority of bridges serve less densely populated, rural locations. This is important because rural bridges often face different challenges in terms of maintenance and funding compared to urban bridges, which might be more frequently used but are fewer in number. The classification highlights the need for specific policy and resource allocation to ensure that rural infrastructure remains safe and effective for transportation needs.