The channel under a bridge is marked with aids from the lateral system. The centerline of the channel is marked on the bridge with __________.

Correct Answer: Option A — a red-and-white octagon

Under the U.S. Aids to Navigation System, bridge channel centerlines are marked by a red-and-white vertically striped diamond or octagon shape. This visual aid assists mariners in identifying the safest passage through the bridge span, ensuring they maintain a central position to avoid structural hazards or shallow water.