If high amount of current flows through the resistor the resistance[property of material] opposes its flow which causes heating effect in resistor and due to low melting point it breaks down and stops the flow of current in the circuit.Thus saves the device from being harmed.

Characteristics of Fuse Wire:

Fuse wire is a thin wire that is used to protect electrical circuits from overloading or short circuits. It is designed to melt and break the circuit when excessive current flows through it. The characteristics of fuse wire are as follows:

1. High Resistivity:
The fuse wire has high resistivity, which means it offers a significant amount of resistance to the flow of electric current. This high resistance helps in limiting the current flow and prevents the circuit from overheating or getting damaged.

2. Low Melting Point:
The fuse wire is made from materials that have a relatively low melting point. This is important because the wire needs to melt quickly and break the circuit when there is a sudden surge of current or a short circuit. By melting at a low temperature, the fuse wire can react rapidly and interrupt the current flow.

3. Protective Function:
The main purpose of a fuse wire is to protect electrical devices and circuits from damage caused by excessive current. When the current exceeds the rated value, the fuse wire melts, and the circuit is broken. This prevents further flow of current and protects the circuit and connected devices from damage.

4. Safety:
Fuse wires are an important safety feature in electrical systems. By melting and breaking the circuit, they prevent overheating, fire, and potential hazards. Fuse wires are easily replaceable, and their failure indicates a fault in the circuit that needs to be addressed before the fuse is replaced.

5. Size and Material Selection:
The size and material of the fuse wire are carefully chosen based on the specific requirements of the circuit. The wire should be thin enough to melt quickly but thick enough to carry the normal operating current without overheating. Common materials used for fuse wires include copper, aluminum, and alloys like silver or tin.

Conclusion:
In conclusion, the correct answer is option 'D' - high resistivity and low melting point. The fuse wire is designed with these characteristics to ensure effective protection against excessive current and to prevent damage to electrical circuits and devices.