Which factor is immaterial for the wire used in electric fuse?
a)	Length	b)	Radius	c)	Material	d)	Current

(a)

Electric fuse is a type of over current protection device.  They are engineered to contribute a negligible amount of extra resistance to the circuits they protect.  This is largely accomplished by making the fuse wire as short as possible.  Fuses are primarily rated as current amperes.  A fuse wire of certain material and gauge will blow at a certain current no matter how long it is.  Since, length is not a factor in current rating the shorter it can be made the less resistance it will have end to end.