The correct answer is A) A navigator fixing a vessel's position by radar can use radar information from one object to fix the position. This is correct because a navigator can use a single radar bearing from one object to fix the vessel's position. By taking a radar bearing to a known object, the navigator can draw a line on the chart representing the direction to that object, and the vessel's position will lie somewhere along that line. This is known as a "single line of position" fix. The other answer choices are incorrect because: B) Using radar bearings is a valid method for fixing a vessel's position; C) The distance to the horizon does not limit the use of radar bearings; and D) Radar bearings from any direction, not just forward of the beam, can be used to fix the position.