The correct answer is C) three black shapes in a vertical line; the highest and lowest are balls, and the middle one is a diamond. This is the correct answer because the International Regulations for Preventing Collisions at Sea (COLREGS) require a vessel servicing a pipeline during the day to display three black shapes in a vertical line, with the highest and lowest being black balls and the middle one being a black diamond. This signal indicates that the vessel is restricted in its ability to maneuver and engaged in an operation that restricts its ability to keep out of the way of other vessels. The other options are incorrect because they do not accurately depict the required signal for a vessel servicing a pipeline. Options A and B do not include the correct combination of black shapes, while option D does not have the required three shapes in a vertical line.