The correct answer is option 4: "When an electrical safety fuse is rated (marked) as 16 A, it means it will be blown (break) if current exceeds 16 A."

A fuse is a safety device that is designed to protect electrical circuits from potential damage caused by excessive current flow. The rating of a fuse refers to the maximum amount of current it can safely handle without breaking. In this case, a fuse rated as 16 A means that it is designed to handle a maximum current of 16 Amperes.

When the current flowing through the fuse exceeds its rated value, it heats up the fuse element. As the temperature of the fuse element increases, it eventually reaches a critical point at which the fuse "blows," interrupting the circuit and preventing further flow of current. This protects the electrical equipment and wiring from damage due to overcurrent.

Therefore, if the current in the circuit exceeds 16 A, the fuse will be blown, breaking the circuit and protecting the electrical components from potential damage. It is important to use fuses with the correct rating to ensure proper protection of the circuitry.