The correct answer is C. A safety device.
A fuse is a safety device that is used to protect electrical circuits from damage caused by overloading or short circuits. It is a small, cylindrical device that contains a thin wire that melts when the current flowing through it exceeds a certain value. This causes the circuit to break, preventing damage to the circuit and the connected equipment.
A load is a device that consumes electrical energy. It can be a light bulb, a motor, or any other device that uses electricity to operate.
A thermopile is a device that converts heat energy into electrical energy. It is made up of a number of thermocouples, which are junctions of two dissimilar metals that produce an electric current when they are heated.
A step-down device is a device that reduces the voltage of an electrical circuit. It is used to connect devices that operate at different voltages.
In the electrical circuit of a house, the fuse acts as a safety device. It protects the circuit and the connected equipment from damage caused by overloading or short circuits.