The correct answer is C) The tug should put a stern line up, leading ahead on the ship. When docking a ship with a single-screw tug assisting on the starboard bow and anticipating the need to hold the bow off against a current, the tug should have a stern line leading ahead on the ship. This configuration allows the tug to effectively push the bow away from the dock and stem the current, while the stern line provides additional control and stability. Having a stern line leading ahead is more effective than using head lines, as it gives the tug more leverage and a better angle to counteract the force of the current on the bow. The other options are incorrect because they do not provide the optimal setup for the tug to hold the bow off against the current. Using multiple head lines (A) or a single head line (D) would not give the tug sufficient control and leverage, while a spring line (B) would not be as effective in pushing the bow away from the dock.