During daylight, what shapes should a vessel servicing a pipeline display?

A vessel servicing a pipeline during daylight is required to display three black shapes arranged in a vertical line. This indication signals to other vessels in the vicinity that the vessel is engaged in activities related to pipeline operations. Following the guidelines outlined in the U.S. Coast Guard's Rules of the Road, the specific configuration of three shapes is designed to ensure that the vessel is visible and its purpose is clear, allowing for safe navigation around it.

The other options suggest different combinations of shapes which are not prescribed for a pipeline service vessel. For instance, shapes such as balls, diamonds, or cones are used for different types of vessels or activities, but they do not apply to the specific scenario of a vessel working on a pipeline. Understanding the correct display of shapes is essential in maritime operations to ensure clarity and safety for all vessels in the area.