Question 150Navigation General

The correct answer is A) a red-and-white octagon. The centerline of a channel under a bridge is typically marked with a red-and-white octagonal daymark on the bridge structure. This helps to visually indicate the center of the navigable channel to vessels passing beneath the bridge. The other answer choices are incorrect because: B) a yellow triangle is used to mark the preferred channel of a bifurcation, C) a black-and-white diamond is used to mark obstructions or danger areas, and D) three white lights would indicate the center of a channel, but this is not the specific marking used on a bridge.