Final answer:
Boats no more than 6 meters in length must be equipped with distress signals, navigation lights, and sound signaling devices for safety and navigation purposes.
Step-by-step explanation:
The question pertains to the safety requirements for boats that are no more than 6 meters in length. According to maritime safety regulations, such boats must be equipped with various safety and navigational signals. These include distress signals to signal for help in case of emergency, navigation lights, which are used to ensure visibility to other vessels during night and poor visibility conditions, and sound signaling devices, which are used in instances such as fog to indicate presence. The complete set of required signals helps to ensure the safety of the vessel and its occupants, and also aids in preventing collisions at sea. Therefore, the correct answer to the question is d. Distress signals, navigation lights, and sound signaling devices.