How does the design of a 'culvert' differ from that of a bridge in hydraulic engineering?

A$)$ A culvert is primarily designed for air flow, while a bridge is for water flow

B$)$ Culverts convey water under a road or railway, while bridges are structures that span over water or other obstacles for passage

C$)$ Culverts are only used in urban settings, whereas bridges are used in rural areas

D$)$ There is no difference; the terms are interchangeable