The best answer is b - span.
A span is the distance between two bridge supports The supports may be towers, columns, or even the wall of a canyon.
There are many kinds of bridges but they all fall into three types namely beam, arch and suspension. The major difference between these three kinds of bridges is the distance that each can cross in a single span.
For example, a modern beam bridge is likely to span a distance of 200 feet, a modern arch can span 800 or 1000feet, and a modern suspension bridge can span up to 7000ft.
