The correct answer is B) A vessel on pilotage duty. According to the International Regulations for Preventing Collisions at Sea (COLREGS), a vessel on pilotage duty is required to keep out of the way of all other vessels. This is because a vessel on pilotage duty may be restricted in its ability to maneuver and requires the right-of-way to safely navigate the waterway. The other options are incorrect because they do not have the same obligation to keep out of the way. A vessel constrained by her draft (A) and a vessel restricted in her ability to maneuver (D) have the right-of-way, but are not required to keep out of the way of all other vessels. A vessel engaged in fishing (C) is required to keep out of the way of vessels not engaged in fishing.