The correct answer is A) distance. The signal letter "R" followed by one or more numbers indicates the distance to the vessel or object being signaled. This is in accordance with the International Code of Signals, which is used to communicate information between vessels at sea. The other answer choices are incorrect because they do not accurately represent the meaning of the "R" signal. Bearing is indicated by the letter "D", visibility is indicated by the letter "V", and a vessel's identity is typically communicated using the vessel's name or call sign, not a signal letter and number.