The correct answer is A) green light. According to the United States Coast Guard Navigation Rules, a mid-channel buoy, if lighted, will show a green light. This is because mid-channel buoys are used to mark the center or fairway of a navigable channel, and green lights are used to indicate the preferred side of a channel to pass a buoy. The other answer choices are incorrect because a flashing red light (B) would indicate a port-hand buoy, a fixed red light (C) would indicate a starboard-hand buoy, and Morse code (D) is not a standard light color or characteristic for a mid-channel buoy.