The fuse is rated at 0.8 A which means that the current will continue flowing through the circuit when the current is limited to 0.8 A. According to ohm's law, \(I = \frac{\mathrm{V} }{\mathrm{R} } \) . First option will give I=80/100=0.8 A which is the rated voltage and the current will flow through the circuit. For second, third and fourth options, currents are I=80/90=0.89, I=80/80=1 A and I=80/70=1.14 A which are greater than the rated current.