Concept:A fuse protects electrical appliances by melting when excessive current flows through it.Explanation:The fuse wire must melt easily before the excess current can damage the appliance.Therefore, a low melting point is essential for fuse wires.If the melting point were high, the wire would not break quickly and the appliance could be damaged.Low electrical resistivity would allow too much current to pass without generating the heat needed to melt the wire.Thus, the key physical property is a low melting point.Answer:D. Low melting point