According to standards, which of the following must adhere to the prescribed regulations for external conductors?

The correct choice highlights that external conductors must adhere to prescribed regulations, largely due to their exposure to environmental conditions and the potential hazards they may encounter. External conductors, such as those running to and from electrical components on a boat, are subjected to factors like moisture, UV radiation, and mechanical stress, which can significantly impact their performance and safety.

Adhering to standards for external conductors ensures that they are durable, properly insulated, and capable of handling the electrical load while minimizing risks like short circuits or electrical fires. These regulations are designed to protect both the electrical system and the people using the vessel, contributing to overall safety and reliability.

Other options refer to components that either do not interact with external conditions in the same way, such as internal cables housed within the system's protective structures or fuses which are used for overcurrent protection but do not represent conductors in the same context. Grounding wires, while critical for safety, have different regulations focused primarily on earth connections and are not categorized with external conductors.