A vessel at anchor will show a __________.

Answer: B — ball

A vessel at anchor is required to display a specific day shape to indicate its status. The correct shape for a vessel at anchor is a black ball, which is shown during daylight hours. This visual signal is important as it informs other vessels in the vicinity that the anchored vessel is not under way and is effectively taking up a position in the water. This convention is part of maritime navigation rules aimed at preventing collisions and maintaining safety on the water. The use of a black ball at anchor helps other mariners recognize the vessel's state, allowing them to navigate accordingly. Understanding the visual signals, such as the black ball for an anchored vessel, is critical for proper maritime practice and adherence to the Rules of the Road.