The correct answer is C) during daylight hours in any visibility. According to the US Coast Guard regulations, all vessels must display identification shapes (such as balls, cones, or cylinders) during daylight hours regardless of the visibility conditions. This requirement applies to both international and inland waters. The purpose of these shapes is to indicate the type and status of the vessel to other mariners. The other answer choices are incorrect because: A) the regulations do not restrict the display of identification shapes to a specific time window; B) the shapes must be displayed during daylight hours in any visibility, not just in unrestricted visibility; and D) the shapes are required during daylight hours, not between sunset and sunrise.