The correct answer is A) a vessel engaged in public safety activities. According to the Inland Navigation Rules, an alternating red and yellow light indicates a vessel engaged in public safety activities, such as law enforcement, search and rescue, or other emergency operations. This light pattern is used to identify these types of vessels so that other mariners can take appropriate actions to avoid interference with their important work. The other options are incorrect because a law enforcement vessel would display a blue light (answer B), a vessel in distress would display a solid red light (answer C), and a vessel restricted in its ability to maneuver would display different lights, such as red and white lights (answer D).