The correct answer is B) range line. A range line is a line of position formed by sighting two charted objects that are in line with each other. This is a common technique used in navigation to determine a vessel's position. The two charted objects are used as range markers, and the line connecting them is the range line, which represents the vessel's position along that line. The other answer choices are incorrect because: A) a track line is the vessel's course over ground, C) an estimated position is a calculated position based on various factors, and D) a relative bearing is the angle between the vessel's heading and the direction of another object.